In a frosty manner (5)
I believe the answer is:
icily
'in a frosty manner' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for icily that I've seen before include "In a frosty manner" , "In a cold manner" , "in unfriendly way" , "In a chilling manner" , "Coldly" .)