Rising star accepts Lethal Weapon but not Fifty Shades (7)
I believe the answer is:
nuances
'not fifty shades' is the definition.
'nuances' can be an answer for 'shades' ('nuance' can be a synonym of 'shade'). I am not certain of the 'not fifty' bit.
'rising star accepts lethal weapon' is the wordplay.
'rising' is a reversal indicator (in a down clue, letters go up).
'star' becomes 'sun' (the Sun is a star).
'accepts' is an insertion indicator.
'lethal weapon' becomes 'ance' (I can't justify this - if you can you should give a lot more credence to this answer).
'sun' in reverse letter order is 'nus'.
'nus' placed around 'ance' is 'NUANCES'.
'but' is the link.
Can you help me to learn more?
(Other definitions for nuances that I've seen before include "subtle shades" , "Subtle differences" , "suggestions" , "Subtleties" , "'Subtle variations, in meaning perhaps (7)'" .)