Small, small person is a pain (6)
I believe the answer is:
stitch
'pain' is the definition.
(pain in the body)
'small small person' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'small person' becomes 'titch' (titch can informally mean a short person).
's'+'titch'='STITCH'
'is a' is the link.
(Other definitions for stitch that I've seen before include "''A . . . . . . in time saves nine'' (6)" , "Use a needle - pain in the side" , "something seen in the needlework class" , "One in time is said to save nine" , "Perform final act in theatre" .)