Harry rowed around one strange fish (6)
I believe the answer is:
weirdo
'strange fish' is the definition.
('strange fish' can informally mean an eccentric)
'harry rowed around one' is the wordplay.
'harry' is an anagram indicator (I've seen this in other clues).
'around' indicates putting letters inside.
'one' becomes 'i' (roman numeral).
'rowed' is an anagram of 'werdo'.
'werdo' placed around 'i' is 'WEIRDO'.
(Other definitions for weirdo that I've seen before include "Derogatory term for an eccentric" , "Crank - oddball" , "Slang for odd or eccentric person" , "Informally eccentric person - sounds spooky" , "Odd type" .)