Estimate, judge (5)
I believe the answer is:
gauge
This clue is a double definition.
'estimate' is the first definition.
(I know that estimate can be written as gauge)
'judge' is the second definition.
(I know that judge can be written as gauge)
(Other definitions for gauge that I've seen before include "Judge" , "Estimate, form judgement of" , "Distance between the rails of a railway track" , "Instrument to measure or test" , "standard size" .)