When it's good and hot outside, leave (3,2)
I believe the answer is:
hop it
'leave' is the definition.
(I've seen this before)
'when it's good and hot outside' is the wordplay.
I cannot quite understand how this works, but
'good' could be 'pi' (old-fashioned term for pious) and 'pi' is found in the answer.
'hot' could be 'h' (abbreviation eg on taps) and 'h' is found in the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found within the answer.
A single letter 'o' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for hop it that I've seen before include "Skedaddle!" , "Run along now!" , "shove off" , "get lost" , "Go away (colloq.)" .)