Mirror? One friend holds it (7)
I believe the answer is:
imitate
'mirror?' is the definition.
(thesaurus)
'one friend holds it' is the wordplay.
'one' becomes 'i' (Roman numeral).
'friend' becomes 'mate' (mate is a kind of friend**).
'holds' is an insertion indicator.
'mate' going around 'it' is 'mitate'.
'i'+'mitate'='IMITATE'
(Other definitions for imitate that I've seen before include "I tame it (anag)" , "Mimic or follow as a model" , "I ate Tim! (anag.)" , "Copy, simulate" , "Fake" .)