Warning of cold front of Arctic temperature, including hail (6)
I believe the answer is:
caveat
'warning' is the definition.
(caveat is a kind of warning)
'cold front of arctic temperature including hail' is the wordplay.
'cold' becomes 'c' (eg on taps).
'front of' suggests taking the first letters.
'including' means one lot of letters goes inside another.
'hail' becomes 'ave' (I've seen this before).
The first letters of 'arctic temperature' is 'at'.
'c'+'at'='cat'
'cat' placed around 'ave' is 'CAVEAT'.
'of' is the link.
(Other definitions for caveat that I've seen before include "Warning (of conditions)" , "Warning in a legal document" , "Caution - qualification" , "A warning against certain acts" , "A notice or warning" .)