Unremitting rise of marijuana suppressed by French denials (3-4)
I believe the answer is:
non-stop
'unremitting' is the definition.
(unremitting can mean relentless or not stopping)
'rise of marijuana suppressed by french denials' is the wordplay.
'rise of' shows that the letters should be reversed in order (in a down clue, letters go up).
'marijuana' becomes 'pot' (slang term for marijuana).
'suppressed by' says to put letters next to each other.
'french denials' becomes 'nons' (I've seen this in another clue).
'pot' written backwards gives 'top'.
'top' put after 'nons' is 'NON-STOP'.
(Other definitions for non-stop that I've seen before include "Round-the-clock" , "continuously" , "Going straight from A to B" , "Continuous" , "Ceaseless" .)