Entrance, using commercial with sex appeal (4)
I believe the answer is:
adit
'entrance' is the definition.
(I've seen this before)
'commercial with sex appeal' is the wordplay.
'commercial' becomes 'ad'.
'with' means one lot of letters go next to another.
'sex appeal' becomes 'it'.
'ad'+'it'='ADIT'
'using' is the link.
(Other definitions for adit that I've seen before include "Mine access passage" , "Pit access" , "Passageway into a mine" , "Horizontal mine drainage shaft" , "Mine opening" .)