Shamefully unruly, only big (7)
I believe the answer is:
ignobly
'shamefully' is the definition.
Both the answer and definition are adverbs. Perhaps you can see an association between them that I don't see?
'unruly only big' is the wordplay.
'unruly' indicates an anagram.
'only'+'big'='onlybig'
'onlybig' is an anagram of 'IGNOBLY'.
Can you help me to learn more?
(Other definitions for ignobly that I've seen before include "In a despicable manner" , "In a dishonourable way" , "Basely" .)