Measure of daytime temperature (4)
I believe the answer is:
mete
'measure' is the definition.
(meting things out is measuring them out)
'of daytime temperature' is the wordplay.
'of' says the answer is hidden in the clue.
'METE' can be found hidden inside 'daytime temperature'.
(Other definitions for mete that I've seen before include "Measure" , "Administer or bestow, as in small portions" , "Give as due - say punishment" , "Administer or hand out" , "Dispense, give (out)" .)