Whistle — or miaow? (7)
I believe the answer is:
I believe this is a double definition.
'whistle' is the first definition.
(I've seen this before)
'miaow?' is the second definition.
(sound made by a cat)
'or' acts as a link.
(Other definitions for catcall that I've seen before include "1express disapproval", "taunt from the audience", "Audibly disapprove", "Barracking", "Audience's expression of disapproval".)