Internal contraction due to extremely speedy boa? (7)
I believe the answer is:
Here is my best explanation:
'internal contraction' is the definition.
'extremely speedy boa?' is the wordplay.
'extremely' suggests removing the centre.
'boa?' becomes 'stole' (both can mean a scarf or shawl).
'speedy' with its middle taken out is 'sy'.
'due to' is the link.