Bringing up a beef gravy initially in need of stirring (8)
I believe the answer is:
grousing
'bringing up a beef' is the definition.
(both can mean complaining)
'gravy initially in need of stirring' is the wordplay.
'gravy initially' becomes 'g' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in need of' means one lot of letters go next to another.
'stirring' becomes 'rousing' (synonyms).
'g'+'rousing'='GROUSING'
(Other definitions for grousing that I've seen before include "continually finding fault" , "Grumbling, bellyaching" .)