So here's a strange sort of fish (3,5)
I believe the answer is:
sea horse
'fish' is the definition.
(sea horse is a kind of fish)
'so here's a strange sort' is the wordplay.
'strange sort' indicates an anagram.
'so'+'heres'+'a'='soheresa'
'soheresa' anagrammed gives 'SEA-HORSE'.
'of' acts as a link.
(Other definitions for sea horse that I've seen before include "Upright fish; so here's a (anag.)" , "Small fish with head like an engine animal" , "Small fish swimming upright" , "Upright swimmer" , "Marine fish" .)