Probably dressing like head of Armani in extravagant fashion (10)

'probably' is the definition.
Both the definition and answer are adverbs. Maybe you can see a link between them that I don't see?

'dressing like head of armani in extravagant fashion' is the wordplay.
'dressing' is an insertion indicator (inserted letters are dressed or clad in others).
'like' becomes 'dig' (to dig can mean to appreciate or 'get').
'head of' says to take the initial letters.
'in extravagant fashion' becomes 'prolly' (I can't explain this - if you can you should give a lot more credence to this answer).
The initial letter of 'armani' is 'a'.
'dig'+'a'='diga'
'diga' going within 'prolly' is 'PRODIGALLY'.

Can you help me to learn more?