Friendly porter seen regularly when working (9)
I believe the answer is:
preseason
'friendly' is the definition.
(eg match before the main football season)
'porter seen regularly when working' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'working' becomes 'on' (on can mean working or activated).
'porter'+'seen'='porterseen'
The alternating letters of 'porterseen' are 'prese'.
'prese'+'as'+'on'='PRESEASON'
(Other definitions for preseason that I've seen before include "period before play starts" , "before the play begins" , "Before league games begin" .)