Join by just accepting the end of bombing (5)
I believe the answer is:
merge
'join' is the definition.
(I've seen this before)
'just accepting the end of bombing' is the wordplay.
'just' becomes 'mere' (I've seen this in other clues).
'accepting' indicates putting letters inside.
'the end of' indicates one should take the final letters.
The last letter of 'bombing' is 'g'.
'mere' going around 'g' is 'MERGE'.
'by' acts as a link.
(Other definitions for merge that I've seen before include "Join into one" , "Become combined" , "Join, blend" , "Combine, coalesce" , "Combine elements" .)