Appraise, estimate the value (6)
I believe the answer is:
assess
This clue is a double definition.
'appraise' is the first definition.
(synonyms)
'estimate the value' is the second definition.
(I've seen this before)
(Other definitions for assess that I've seen before include "Estimate value (for tax)" , "Estimate the worth or quality of" , "Reckon value" , "Test" , "Evaluate (quality)" .)