Fish with a line? Perfect (5)
I believe the answer is:
ideal
'perfect' is the definition.
('ideal' can be similar in meaning to 'perfect')
'fish with a line?' is the wordplay.
'fish' becomes 'ide' (I've seen this before**).
'with' says to put letters next to each other.
'line?' becomes 'l'.
'ide'+'a'+'l'='IDEAL'
(Other definitions for ideal that I've seen before include "immaculate" , "Paragon" , "Perfect but perhaps unlikely to become reality" , "Perfect; visionary" , "Conceptual" .)