"Fish" is no good in beer!
I believe the answer is:
'fish' is the definition.
('angle' can be a synonym of 'fish')
'no good in beer' is the wordplay.
'no' becomes 'n' (common abbreviation).
'good' becomes 'g' (abbreviation).
'in' indicates putting letters inside.
'beer' becomes 'ale' (I've seen this before).
'ng' going within 'ale' is 'ANGLE'.
'is' is the link.
(Other definitions for angle that I've seen before include "Standpoint" , "Fish; viewpoint" , "Early settler" , "Point of view - associated with Saxon" , "Opinion" .)