Do held by sailor and blokes showing belly (7)
I believe the answer is:
abdomen
'belly' is the definition.
(synonyms)
'do held by sailor and blokes' is the wordplay.
'held by' means one lot of letters goes inside another.
'sailor' becomes 'ab' (abbreviation for able seaman).
'and' is a charade indicator (letters next to each other).
'blokes' becomes 'men' (I've seen this in other clues).
'ab'+'men'='abmen'
'do' going into 'abmen' is 'ABDOMEN'.
'showing' is the link.
(Other definitions for abdomen that I've seen before include "Insect's body part" , "Central part of the body" , "pot" , "Region of the body between the thorax and pelvis" , "guts" .)