Male in commercial with it is let in (5)
I believe the answer is:
admit
'is let in' is the definition.
(I've seen this before)
'male in commercial with it' is the wordplay.
'male' becomes 'm' (common abbreviation).
'in' means one lot of letters goes inside another.
'commercial' becomes 'ad' (abbreviation for advertisement).
'with' says to put letters next to each other.
'ad'+'it'='adit'
'm' inserted within 'adit' is 'ADMIT'.
(Other definitions for admit that I've seen before include "Take on" , "Usher in" , "Let in - concede" , "Accept" , "Disclose" .)