Cosmetic, perhaps a brand mum gets hold of (7)
I believe the answer is:
mascara
'cosmetic' is the definition.
(mascara is a kind of cosmetic)
'a brand mum gets hold of' is the wordplay.
'brand' becomes 'scar' (I've seen this before**).
'mum' becomes 'ma' ('ma' can be a synonym of 'mum').
'gets hold of' means one lot of letters goes inside another.
'a'+'scar'='ascar'
'ascar' going inside 'ma' is 'MASCARA'.
'perhaps' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.
(Other definitions for mascara that I've seen before include "that accentuates lashes" , "facial cosmetic" , "could be found in handbag, perhaps" , "Eyelash darkener" , "Maracas (anag.)" .)