Jumper, sensible to trap moderate warmth inside (4,11)
I believe the answer is:
room temperature
'warmth inside' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'jumper sensible to trap moderate' is the wordplay.
I cannot really see how this works, but
'jumper' could be 'roo' (short for kangaroo, something which jumps) and 'roo' is found in the answer.
'moderate' could be 'temper' (synonyms) and 'temper' is present in the answer.
'sensible' could be 'mature' (I've seen this before) and 'mature' is found in the leftover letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for room temperature that I've seen before include "Degree of heat" , "not very heated" , "around seventy" .)