Son, crazy, with a rash look? (6)
I believe the answer is:
spotty
'with a rash look?' is the definition.
(having spots or a rash)
'son crazy' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'crazy' becomes 'potty' (I've seen this before).
's'+'potty'='SPOTTY'
(Other definitions for spotty that I've seen before include "Covered in rash" , "With skin blemishes" , "Covered in blotches" , "Pimply or covered with dots" , "Covered in acne" .)