Freezing time limit involves elderly Poles (4,4)
I believe the answer is:
cold snap
'freezing time' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'limit involves elderly poles' is the wordplay.
'limit' becomes 'cap' (capping is a kind of limiting).
'involves' is an insertion indicator.
'elderly' becomes 'old' (similar in meaning).
'poles' becomes 'SN' (North and South poles).
'old'+'sn'='oldsn'
'cap' placed around 'oldsn' is 'COLD SNAP'.
Can you help me to learn more?
(Other definitions for cold snap that I've seen before include "Short spell of severe frost" , "Spell when it isn't like 8" , "Brief spell of freezing weather" , "Period of icy weather" , "Sudden chilly period" .)