Heavy wig they are adjusting (7)
I believe the answer is:
'heavy' is the definition.
(I know that heavy can be written as weighty)
'wig they are adjusting' is the wordplay.
'are adjusting' is an anagram indicator.
'wigthey' anagrammed gives 'WEIGHTY'.
(Other definitions for weighty that I've seen before include "having great influence" , "Important" , "significant" , "substantial" , "Cumbersome" .)