Depict harbour fish (7)
I believe the answer is:
portray
'depict' is the definition.
('portray' can be a synonym of 'depict')
'harbour fish' is the wordplay.
'harbour' becomes 'port' (I've seen this before).
'fish' becomes 'ray' (ray is a kind of fish).
'port'+'ray'='PORTRAY'
(Other definitions for portray that I've seen before include "Use words to describe" , "Show" , "Delineate" , "Paint a picture" , "Depict in art" .)