Running time required by commercial (5)
I believe the answer is:
admin
'running' is the definition.
(I've seen this before)
'time required by commercial' is the wordplay.
'time' becomes 'min' (**).
'required by' says to put letters next to each other.
'commercial' becomes 'ad'.
'min' put after 'ad' is 'ADMIN'.
(Other definitions for admin that I've seen before include "Process of running an organisation (abbr)" , "Management (abbr.)" , "Organisation (colloq.)" , "Business organisers" , "Business management" .)