Dirty, like the little boy's clothes (4)
I believe the answer is:
blue
This clue might be a double definition.
'dirty' is the first definition.
(blue can mean pornographic)
'the little boy's clothes' is the second definition.
'blue' can be an answer for 'clothes' (blue is a kind of clothes). I'm unsure of the 'the little boy's' bit.
'like' is the link.
Can you help me to learn more?
(Other definitions for blue that I've seen before include "and 17 World's largest mammal" , "This movie is X-rated" , "coarse" , "in Oxford, it's dark" , "Colour; depressed" .)