One at school during the winter months? (4)
I believe the answer is:
term
'one at school' is the definition.
The definition and answer can be both related to thinking as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'during the winter months?' is the wordplay.
'during' indicates the answer is hidden within the clue.
'TERM' is hidden within 'winter months'.
Can you help me to learn more?
(Other definitions for term that I've seen before include "Word; trimester" , "Through which something has got to last" , "School time; word" , "A period, esp. of schooling" , "Word; limited period" .)