Concerns small stroke (6)
I believe the answer is:
caress
'stroke' is the definition.
(I know that caress is a type of stroke)
'concerns small' is the wordplay.
'concerns' becomes 'cares' ('care' can be a synonym of 'concern').
'small' becomes 's' (abbreviation - e.g. clothes size).
'cares'+'s'='CARESS'
(Other definitions for caress that I've seen before include "pet" , "Gentle affectionate stroking" , "Scares with loving stroke" , "Gentle stroke" , "Touch with affection" .)