Senseless desire to get on (6)
I believe the answer is:
wanton
'senseless' is the definition.
(I've seen this in another clue)
'desire to get on' is the wordplay.
'desire' becomes 'want' (want is a kind of desire).
'to get' is a charade indicator (letters next to each other).
'want'+'on'='WANTON'
(Other definitions for wanton that I've seen before include "Irresponsible like vandal, lacking proper motives" , "Wilful - promiscuous" , "Dissolute and promiscuous" , "Libertine" , "Thoughtlessly and unnecessarily cruel" .)