Sport held back by Benito Mussolini (4)
I believe the answer is:
sumo
'sport' is the definition.
(I've seen this before)
'held back by benito mussolini' is the wordplay.
'back by' is a reversal indicator.
'held' indicates a hidden word.
'omus' can be found hidden inside 'benito mussolini'.
'omus' in reverse letter order is 'SUMO'.
(Other definitions for sumo that I've seen before include "Japanese wrestling for huge men" , "foreign form of fighting" , "Large Japanese wrestler" , "Kind of wrestling" , "Style of traditional Japanese wrestling" .)