Guardian article on haircare product (5)
I believe the answer is:
angel
'guardian' is the definition.
(guardian angel)
'article on haircare product' is the wordplay.
'article' becomes 'an' (indefinite article).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'haircare product' becomes 'gel' (hair gel).
'an'+'gel'='ANGEL'
(Other definitions for angel that I've seen before include "Cloud resident?" , "Messenger < is a nurse" , "Glean (anag.)" , "Seraph or cherub?" , "Messenger of God" .)