Mostly cold, can give a hot effect (5)
I believe the answer is:
spice
'give a hot effect' is the definition.
The definition and answer can be both human attributes as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'mostly cold' is the wordplay.
'mostly' becomes 'sp' (I can't justify this - if you can you should believe this answer much more).
'cold' becomes 'ice' (I've seen this before).
'sp'+'ice'='SPICE'
'can' acts as a link.
Can you help me to learn more?
(Other definitions for spice that I've seen before include "Aromatic flavouring" , "Something providing excitement" , "Eg, cinnamon" , "Pungent substance to flavour food" , "Eg, turmeric" .)