Small cuckoo may be mottled (6)
I believe the answer is:
spotty
'be mottled' is the definition.
(thesaurus)
'small cuckoo' is the wordplay.
I cannot really understand how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is found within the answer.
The remaining letters 'potty' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'may' acts as a link.
Can you help me to learn more?
(Other definitions for spotty that I've seen before include "Adolescent boys are often so" , "Pimply or covered with dots" , "With skin blemishes" , "Freckled" , "Inconsistent" .)