Location of fish, say (5)
I believe the answer is:
place
'location' is the definition.
(a location is a place)
'fish say' is the wordplay.
'fish' becomes 'plaice' (plaice is a kind of fish).
'say' shows a homophone (sound like).
'plaice' is a homophone of 'PLACE'.
'of' acts as a link.
(Other definitions for place that I've seen before include "Locality" , "Venue" , "Spot" , "Put in - winning position" , "Endearingly pretty" .)