Do an impression of one friend with grasp of Italian (7)
I believe the answer is:
imitate
'do an impression of' is the definition.
(I've seen this in another clue)
'one friend with grasp of italian' is the wordplay.
'one' becomes 'i' (Roman numeral).
'friend' becomes 'mate' (mate is a kind of friend).
'with grasp of' is an insertion indicator.
'italian' becomes 'it' (abbreviation for Italian).
'mate' enclosing 'it' is 'mitate'.
'i'+'mitate'='IMITATE'
(Other definitions for imitate that I've seen before include "Mock" , "Follow suit" , "Reproduce" , "I tame it (anag)" , "Copy or mimic" .)