Short of money, regularly taking stimulants? (2,4,6)
I believe the answer is:
on ones uppers
'short of money' is the definition.
'regularly taking stimulants?' is the wordplay.
I cannot quite understand how this works, but
'taking' could be 'on' (eg one taking drugs is 'on' drugs) and 'on' is found within the answer.
This explanation may well be incorrect...
(Other definitions for on ones uppers that I've seen before include "Very short of money" , "when skint?" , "Where to rub 9 [CHERRY BLOSSOM]" , "Impecunious" .)