Pub hosts fellow with ukulele, initially as a joke (2,3)
I believe the answer is:
in fun
'as a joke' is the definition.
(I've seen this before)
'pub hosts fellow with ukulele initially' is the wordplay.
'pub' becomes 'inn' (an inn is a type of pub).
'hosts' indicates putting letters inside (inserted letters are welcomed or hosted).
'fellow with' becomes 'f' (I've seen this in other clues).
'initially' suggests taking the first letters.
The initial letter of 'ukulele' is 'u'.
'f'+'u'='fu'
'inn' going around 'fu' is 'IN FUN'.
(Other definitions for in fun that I've seen before include "to raise a smile?" , "for a laugh" , "As a joke - not seriously" , "Not intended seriously" .)