No simple answer, as far as I know.
You can also just click on the Disclosure Triangles (small, barely visible upward facing triangles in the line at the bottom of the View) to display all files included in the level of the View that you are sitting at, or the selected items in the top pane.
There is no standard Composers View, so it must be a View you built. I was looking at the standard Genre View, which is a Categories View with the defined levels of "Genre > Album Artist Auto > Album", and I found that if I double-clicked a Genre which contained multiple Albums from one Album Artist, when I double-clicked on most Album Artists the Albums were shown in the top pane and the file details were shown in the bottom pane for all Albums. But for some values of [Album Artist (auto)] the bottom pane was not opened.
I couldn't see any reason for the Genre View behaving that way. It sounds like you Composer View is behaving in a similar way, except that the bottom details pane is never opening.
You could try comparing the standard Artists View definition to your Composer View and see if anything is obviously different. Although in the case of the Genre View above, the behaviour seemed to be data driven, and not based on the VIew definition.
Anyway, just use the Disclosure Triangles, or if you want a better answer, share the View definition for your Composers View. Someone may have a better answer.
PS: When the details aren't displayed, playback is probably starting because you have the double-click behaviour in "Options > General > Behaviour > Double-click" set to "Add to Playing Now (play now)". But for that to happen, MC has to have decided that you have selected all the files for the Composer, or the Album if you are talking about that level in the View, rather than just selecting the Album to display the Tracks. Strange behaviour. Well, in my Genres View anyway.
