On holiday, with reserve in place of business (6)
I believe the answer is:
office
'place of business' is the definition.
(office is a kind of place of business)
'on holiday with reserve' is the wordplay.
'on holiday' becomes 'off' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'reserve' becomes 'ice' (I've seen this before).
'off'+'ice'='OFFICE'
'in' is the link.
(Other definitions for office that I've seen before include "Subsidiary" , "Official position" , "Department" , "Business room or religious rite" , "Box ---, ticket agency" .)