Half-bloods complete breather for a whale (8)
I believe the answer is:
blowhole
'breather for a whale' is the definition.
I can't tell whether this definition defines the answer.
'half-bloods complete' is the wordplay.
'half' suggests halving the letters.
'complete' becomes 'whole' (associated in meaning).
'bloods' cut in half is 'blo'.
'blo'+'whole'='BLOWHOLE'
Can you help me to learn more?
(Other definitions for blowhole that I've seen before include "Nostril of whale or dolphin on the top of its head" , "Whale's nostril" , "Opening for the escape of gas or air" , "escape route from tunnel" .)