Models belt him with a sewing aid (7)
I believe the answer is:
thimble
'a sewing aid' is the definition.
(I've seen this in another clue)
'models belt him' is the wordplay.
'models' indicates an anagram.
'belt'+'him'='belthim'
'belthim' anagrammed gives 'THIMBLE'.
'with' acts as a link.
(Other definitions for thimble that I've seen before include "Sewer's protection" , "Protective item for the tailor" , "sewer cover?" , "Cap used for protection when sewing" , "Needlewoman's aid" .)