Stress is negligible taking cannabis (9)
I believe the answer is:
spotlight
'stress' is the definition.
(spotlighting is a kind of stressing)
'negligible taking cannabis' is the wordplay.
'negligible' becomes 'slight'.
'taking' means one lot of letters goes inside another.
'cannabis' becomes 'pot' ('pot' can be a synonym of 'cannabis').
'slight' going around 'pot' is 'SPOTLIGHT'.
'is' is the link.
(Other definitions for spotlight that I've seen before include "Lit up in public here" , "exposure" , "fame" , "Illumination focused on small area" , "Beam directed on small area or on stage performer" .)