US drugs agent getting increasingly high on New York's crack (6)
I believe the answer is:
cranny
'crack' is the definition.
(I know that crack can be written as cranny)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for cranny that I've seen before include "Fissure - chink" , "confined space" , "Secret place (searched after nook)" , "Crack" , "Small narrow space" .)