My sonny, screwing up small coats, hides? (8)
I believe the answer is:
synonyms
'coats hides?' is the definition.
('coats' and 'hides' are synonyms of each other)
'my sonny screwing up small' is the wordplay.
'screwing up' is an anagram indicator.
'small' becomes 's' (abbreviation - e.g. clothes size).
'my'+'sonny'='mysonny'
'mysonny' is an anagram of 'synonym'.
'synonym'+'s'='SYNONYMS'
(Other definitions for synonyms that I've seen before include "words such as faith, religion and belief" , "Two words that can be interchanged" , "Interchangeable words" , "Two words with the same meaning" , "Words with meanings similar to those of others" .)