A passionate knight going out is fragrant (8)
I believe the answer is:
aromatic
'fragrant' is the definition.
('aromatic' can be similar in meaning to 'fragrant')
'a passionate knight going out' is the wordplay.
'passionate' becomes 'romantic' (I've seen this before).
'knight' becomes 'n' (chess).
'going out' is a deletion indicator.
'romantic' with 'n' taken away is 'romatic'.
'a'+'romatic'='AROMATIC'
'is' acts as a link.
(Other definitions for aromatic that I've seen before include "Spicy material" , "Cairo mat may smell nice" , "smelling nice" , "scent" , "Pleasant-smelling" .)