Remove frost around head of vital instrument (6)
I believe the answer is:
device
'instrument' is the definition.
(I've seen this before)
'remove frost around head of vital' is the wordplay.
'remove' becomes 'de' (I've seen this in other clues).
'frost' becomes 'ice' (synonyms).
'around' indicates putting letters inside.
'head of' indicates taking the first letters.
The first letter of 'vital' is 'v'.
'de'+'ice'='deice'
'deice' going around 'v' is 'DEVICE'.
(Other definitions for device that I've seen before include "something mechanical?" , "Gadget, tool, piece of equipment" , "Plan - emblem" , "Scheme, trick; item of equipment" , "Trick; heraldic design" .)