Fish left in straw hats (8)
I believe the answer is:
bloaters
'fish' is the definition.
(I've seen this before)
'left in straw hats' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in' is an insertion indicator.
'straw hats' becomes 'boaters' ('boater' can be a synonym of 'straw hat').
'l' inserted inside 'boaters' is 'BLOATERS'.
(Other definitions for bloaters that I've seen before include "smoked herring" , "Smoked herrings from Yarmouth" , "fish" .)