Small, small person may be cross (6)
I believe the answer is:
stitch
'be cross' is the definition.
(cross stitch is a type of stitch)
'small small person' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'small person' becomes 'titch' (titch can informally mean a small person).
's'+'titch'='STITCH'
'may' is the link.
(Other definitions for stitch that I've seen before include "Pain for runner" , "result of working with needle?" , "Sharp spasm of pain in the side" , "Something surgeon provides" , "Sudden pain in side after exercise" .)