"Fish" is no good in beer! (5)
I believe the answer is:
angle
'fish' is the definition.
(angle can mean to fish)
'no good in beer' is the wordplay.
'no good' becomes 'ng' (abbreviation).
'in' indicates putting letters inside.
'beer' becomes 'ale' (type of beer).
'ng' inserted inside 'ale' is 'ANGLE'.
'is' acts as a link.
(Other definitions for angle that I've seen before include "Standpoint" , "Fish; viewpoint" , "Early settler" , "Point of view - associated with Saxon" , "Opinion" .)