Back or rump or bits of sow's entrails (7)
I believe the answer is:
endorse
'back' is the definition.
('endorse' can be a synonym of 'back')
'rump or bits of sow's entrails' is the wordplay.
'rump' becomes 'end'.
'bits of' says to take the initial letters.
The initial letters of 'sows entrails' is 'se'.
'end'+'or'+'se'='ENDORSE'
'or' acts as a link.
(Other definitions for endorse that I've seen before include "Champion" , "Say you approve" , "Corroborate" , "Give support or approval to" , "Back, sanction" .)