Object to holiday in New Guinea initially (5)
I believe the answer is:
thing
'object' is the definition.
(an object is a thing or item)
'to holiday in new guinea initially' is the wordplay.
'initially' suggests taking the first letters.
The first letters of 'to holiday in new guinea' is 'THING'.
(Other definitions for thing that I've seen before include "Object; gadget" , "Object, artefact" , "Affair - matter" , "Individual unit" , "cup of tea" .)