Passionate knight leaves showy clothing (5)
I believe the answer is:
fiery
'passionate' is the definition.
('fiery' can be similar in meaning to 'passionate')
'knight leaves showy clothing' is the wordplay.
'knight' becomes 'n' (chess).
'leaves' indicates named letters should be taken away.
'showy clothing' becomes 'finery' (I've seen this before).
'finery' with 'n' taken away is 'FIERY'.
(Other definitions for fiery that I've seen before include "Choleric" , "Impetuous; hot-tasting" , "Hot-tempered, passionate" , "Quick-tempered" , "Inflamed" .)