Ape I note by gallery (7)
I believe the answer is:
imitate
'ape' is the definition.
(synonyms)
'i note by gallery' is the wordplay.
'note' becomes 'mi' (as in 'do re mi').
'by' is a charade indicator (letters next to each other).
'gallery' becomes 'tate' (Tate Modern, Tate Britain etc).
'i'+'mi'+'tate'='IMITATE'
(Other definitions for imitate that I've seen before include "Mock" , "Appear like, in behaviour or appearance" , "Copy someone" , "Reproduce" , "I ate Tim! (anag.)" .)