Half-Vulcan box contains head of Prometheus (5)
I believe the answer is:
spock
'half-vulcan' is the definition.
(Mr Spock from Star Trek is half-Vulcan)
'box contains head of prometheus' is the wordplay.
'box' becomes 'sock' (both can mean to hit).
'contains' is an insertion indicator.
'head of' suggests taking the first letters.
The first letter of 'prometheus' is 'p'.
'sock' placed around 'p' is 'SPOCK'.
(Other definitions for spock that I've seen before include "In terms of childcare, a revolutionary" , "Star Trek Vulcan" , "aka Leonard Nimoy" , "Star Trek character" .)