Such a frost means the house needs a bit of warmth (4)
I believe the answer is:
hoar
'such a frost' is the definition.
(synonyms)
'the house needs a bit of warmth' is the wordplay.
'the house' becomes 'h'.
'needs' means one lot of letters go next to another.
'a bit of warmth' becomes 'oar' (I can't explain this - if you can you should believe this answer much more).
'h'+'oar'='HOAR'
'means' acts as a link.
Can you help me to learn more?
(Other definitions for hoar that I've seen before include "Here are ice crystals" , "Grey with age; frost" , "Type of frost" , "A kind of white frost" , "Greyish-white with age or frost" .)