Support staff kept back in quarters (7)
I believe the answer is:
endorse
'support' is the definition.
(endorsing is a kind of supporting)
'staff kept back in quarters' is the wordplay.
'staff' becomes 'rod' (both can mean a stick or cane).
'kept back' shows that the letters should be reversed in order.
'in' indicates putting letters inside.
'quarters' becomes 'ENSE' (four quarters of the compass).
'rod' written backwards gives 'dor'.
'dor' placed inside 'ense' is 'ENDORSE'.
(Other definitions for endorse that I've seen before include "Give one's approval to" , "Advocate" , "Approve - support" , "Red ones (anag.)" , "Approve of, sign on back as of cheque" .)