Purposeless
I believe the answer is:
adrift
'purposeless' is the definition.
(similar in meaning)
This is the entire clue.
(Other definitions for adrift that I've seen before include "Unanchored at sea" , "Not anchored, floating freely" , "'Directionless, floating freely (6)'" , "Afloat without control" , "Unsettled or unanchored" .)