Make an entrance under it after a fashion (7)
I believe the answer is:
intrude
'make an entrance' is the definition.
(eg intruding into a building)
'under it after a fashion' is the wordplay.
'after a fashion' indicates an anagram (letters re-fashioned).
'under'+'it'='underit'
'underit' is an anagram of 'INTRUDE'.
(Other definitions for intrude that I've seen before include "Gatecrash" , "Join in without being invited or wanted" , "Come in without invitation" , "Push in unwantedly" , "Pry" .)