Complain about BBC English (4)

I believe the answer is:
carp
'complain' is the definition.
(carp can informally mean to complain or whinge)
'about bbc english' is the wordplay.
I cannot really understand how this works, but
'about' could be 'ca' (abbreviation for circa) and 'ca' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for carp that I've seen before include "Fish; find fault continually" , "Raise trivial objections" , "Fish - grouse" , "ish" , "Go on at" .)
