Put in the ground when it's seasonally cold inside (5)
I believe the answer is:
inter
'put in the ground' is the definition.
(I've seen this in another clue)
'it's seasonally cold inside' is the wordplay.
'it's seasonally' becomes 'int' (I am not sure about this - if you are sure you should believe this answer much more).
'cold' becomes 'zero' (I've seen this before).
'inside' says to take the centre.
The middle of 'zero' is 'er'.
'int'+'er'='INTER'
'when' is the link.
Can you help me to learn more?
(Other definitions for inter that I've seen before include "Prefix for between - bury it" , "Lay to rest" , "Put underground" , "Milan FC" , "Put under the earth" .)