Complaining bitterly, phone about trouble (7)
I believe the answer is:
railing
'complaining bitterly' is the definition.
(I've seen this before)
'phone about trouble' is the wordplay.
'phone' becomes 'ring' ('ring' can be a synonym of 'phone').
'about' is an insertion indicator.
'trouble' becomes 'ail' ('ail' can be a synonym of 'trouble'**).
'ring' going around 'ail' is 'RAILING'.
(Other definitions for railing that I've seen before include "Banter" , "Barrier, balustrade" , "Iron barrier" , "Mocking" , "complaints procedure?" .)