Name adopted by extremely clever crime writer (8)
I believe the answer is:
chandler
'crime writer' is the definition.
(Raymond Chandler was a crime novelist)
'name adopted by extremely clever' is the wordplay.
'name' becomes 'handle' (a handle is a name).
'adopted by' means one lot of letters goes inside another (I've seen this in other clues).
'extremely' says to hollow out the word (remove centre letters) (only the extremes of the word are used).
'clever' with its middle removed is 'cr'.
'handle' placed into 'cr' is 'CHANDLER'.
(Other definitions for chandler that I've seen before include "Supplier of ships' equipment" , "Retailer" , "'Raymond ..., US thriller writer (8)'" , "Boat supplies seller" , "General dealer" .)