Tube blown when blood banks cool (8)
I believe the answer is:
clarinet
'tube blown' is the definition.
I can't judge whether this defines the answer.
'blood banks cool' is the wordplay.
'blood' becomes 'claret' (claret can informally mean blood).
'banks' is an insertion indicator (bank can mean to surround or border).
'cool' becomes 'in' ('in' can mean fashionable or cool).
'claret' placed around 'in' is 'CLARINET'.
'when' is the link.
Can you help me to learn more?
(Other definitions for clarinet that I've seen before include "Single reed woodwind instrument" , "Blow that!" , "It's for playing" , "Woodwind instrument - Artie Shaw played one" , "member of orchestra" .)