Sun hats do disguise many (9)
I believe the answer is:
thousands
'many' is the definition.
(thesaurus)
'sun hats do disguise' is the wordplay.
'disguise' is an anagram indicator (I've seen 'disguising' mean this).
'sun'+'hats'+'do'='sunhatsdo'
'sunhatsdo' anagrammed gives 'THOUSANDS'.
(Other definitions for thousands that I've seen before include "large sum?" , "Large numbers" , "Crowds" , "1000s" , "a lot" .)