Slumber party on boat? (4)
I believe the answer is:
doss
'slumber' is the definition.
(thesaurus)
'party on boat?' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'on' says to put letters next to each other.
'boat?' becomes 'ss'.
'do'+'ss'='DOSS'
(Other definitions for doss that I've seen before include "Sleep (in cheap lodgings?)" , "Sleep in a makeshift bed" , "go to bed" , "In slang, sleep on sods" , "easily accomplished" .)