British educational foundation's reaction to freeze? (4)
I believe the answer is:
brrr
'reaction to freeze?' is the definition.
(exclamation expressing the speaker is cold)
'british educational foundation's' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'educational foundation' becomes 'rrr' (the three R's: writing, reading, arithmetic).
'b'+'rrr'='BRRR'
(Other definitions for brrr that I've seen before include "Complaint about cold" , "cold response" , "Indication of iciness" , "Cold person's exclamation" , "How freezing" .)