Remember this smell? It has no real effect (7)
I believe the answer is:
placebo
'effect' is the definition.
(I have seen 'An effect' mean 'placebo' so perhaps 'effect' could also mean 'placebo')
'remember this smell?' is the wordplay.
'remember' becomes 'place' (I've seen this in another clue).
'this smell?' becomes 'bo' (abbreviation for Body Odour).
'place'+'bo'='PLACEBO'
'it has no real' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for placebo that I've seen before include "Inert pill" , "Harmless substance as medicine to sooth patient" , "Ineffective substance given to humour patient" , "Sham medicine used in test or for effect" , "Prescription to soothe" .)