Sailor joins party workers in the middle? (7)
I believe the answer is:
abdomen
'the middle?' is the definition.
(thesaurus)
'sailor joins party workers' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'joins' says to put letters next to each other.
'party' becomes 'do' (do is a kind of party).
'workers' becomes 'men' (man is a kind of worker).
'ab'+'do'+'men'='ABDOMEN'
'in' acts as a link.
(Other definitions for abdomen that I've seen before include "Central part of the body" , "pot" , "Belly" , "4 part of insect" , "Tummy" .)