One in lower temperature used as a strainer (8)
I believe the answer is:
colander
'a strainer' is the definition.
(colander is a kind of strainer)
'one in lower temperature' is the wordplay.
'one' becomes 'an' (an apple is one apple).
'in' indicates putting letters inside.
'lower temperature' becomes 'colder' (I can't explain this - if you can you should believe this answer much more).
'an' going into 'colder' is 'COLANDER'.
'used as' acts as a link.
Can you help me to learn more?
(Other definitions for colander that I've seen before include "Leaky vessel" , "Culinary strainer" , "Kitchen strainer" , "Straining pan" , "Container for straining water from food" .)