Hair thickener Cliff brought into male support group (7)
I believe the answer is:
mascara
'hair thickener' is the definition.
The definition suggests a singular noun which matches the answer.
'cliff brought into male support group' is the wordplay.
'cliff' becomes 'scar' (I've seen this in another clue).
'brought into' indicates putting letters inside.
'male' becomes 'm' (common abbreviation).
'support group' becomes 'aa' (Alcoholics Anonymous).
'm'+'aa'='maa'
'scar' going inside 'maa' is 'MASCARA'.
Can you help me to learn more?
(Other definitions for mascara that I've seen before include "Make-up for eyelashes" , "could be found in handbag, perhaps" , "Cosmetic for the eyes" , "black application" , "Eyelash cosmetic" .)