Complain about (6)
'complain about' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bemoan that I've seen before include "Deplore, lament" , "Complain about, lament" , "Regret, lament" , "Lament, grieve" .)
(Other definitions for carp that I've seen before include "Complain like goldfish" , "ish" , "Fish often kept in ponds" , "Keep complaining" , "Fish - complain" .)