Not quite a place to catch opera motif (5)

I believe the answer is:

theme

I'm a little stuck... Click here to teach me more about this clue!

'motif' is the definition.
(I know that motif can be written as theme)

I don't understand the rest of the clue.

(Other definitions for theme that I've seen before include "Recurring melody" , "(Writer's) topic" , "[(type of) PARK]" , "Melody on which variations are constructed" , "notedly subject to variation" .)

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app