Drug securing one new meaning (5)
I believe the answer is:
point
'meaning' is the definition.
(point is a kind of meaning)
'drug securing one new' is the wordplay.
'drug' becomes 'pot' (pot is a kind of drug).
'securing' indicates putting letters inside.
'one new' becomes 'in' (I've seen this in other clues).
'pot' going around 'in' is 'POINT'.
(Other definitions for point that I've seen before include "Indicate - off-side fielding position" , "Importance < of level" , "Sharp or tapering end" , "Significance" , "Sharp end - purpose" .)