Paint a picture of harbour fish (7)
I believe the answer is:
portray
'paint a picture' is the definition.
(I've seen this before)
'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'
'of' is the link.
(Other definitions for portray that I've seen before include "Depict in art" , "Use words to describe" , "Paint a picture" , "sketch" , "Act" .)