All together, once resolved to accept cover for bail (2,4)
I believe the answer is:
en bloc
'all together' is the definition.
(I've seen this before)
'once resolved to accept cover for bail' is the wordplay.
'resolved' indicates anagramming the letters.
'to accept' means one lot of letters goes inside another.
'cover for' says to hollow out the word (remove centre letters).
'bail' with its middle removed is 'bl'.
'once' anagrammed gives 'enoc'.
'enoc' placed around 'bl' is 'EN BLOC'.
(Other definitions for en bloc that I've seen before include "All together, en masse" , "in wholesale fashion" , "Wholesale, as one unit" , "As a group (French)" , "All together - as a whole" .)