A bit dirty, caught in some light (4)
I believe the answer is:
racy
'a bit dirty' is the definition.
'caught in some light' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'in' indicates putting letters inside.
'some light' becomes 'ray' (ray is a kind of light).
'c' put inside 'ray' is 'RACY'.
(Other definitions for racy that I've seen before include "Slightly indecent" , "bawdy quality" , "rather blue" , "Spicy" , "Suggestive; spirited" .)