Part of goal to annoy lawyers (8)
I believe the answer is:
crossbar
'part of goal' is the definition.
('crossbar' is part of 'goal')
'annoy lawyers' is the wordplay.
'annoy' becomes 'cross'.
'lawyers' becomes 'bar' (I've seen this before).
'cross'+'bar'='CROSSBAR'
'to' acts as a link.
(Other definitions for crossbar that I've seen before include "One of two on football field" , "Horizontal piece, on a bicycle say" , "Bit of sports equipment" , "It's over the goalie's head" , "Horizontal beam on goalposts" .)