Drunk captain I jettisoned in sleep (6)
I believe the answer is:
catnap
'sleep' is the definition.
(I know this)
'drunk captain i jettisoned' is the wordplay.
'drunk' indicates anagramming the letters.
'jettisoned' is a deletion indicator.
'captain' with 'i' taken away is 'captan'.
'captan' with letters rearranged gives 'CATNAP'.
'in' acts as a link.
(Other definitions for catnap that I've seen before include "little snooze" , "Brief time out" , "Drop off" , "Forty winks (for moggy?)" , "go out briefly" .)