Responsibility deacon usually carries (4)
I believe the answer is:
onus
'responsibility' is the definition.
(onus is a duty or responsibility)
'deacon usually carries' is the wordplay.
'carries' indicates the answer is hidden within the clue.
'ONUS' can be found hidden inside 'deacon usually'.
(Other definitions for onus that I've seen before include "'Burden, load (4)'" , "'Burden, of proof (4)'" , "Burden, duty" , "Capulet opponent (R&J)" , "Liability" .)