Analyse a singular state (5)
I believe the answer is:
assay
'analyse' is the definition.
(assaying is a kind of analysing)
'a singular state' is the wordplay.
'singular' becomes 's' (abbreviation sometimes used in dictionaries).
'state' becomes 'say' ('say' can be a synonym of 'state'**).
'a'+'s'+'say'='ASSAY'
(Other definitions for assay that I've seen before include "Analyse ore for metal content" , "Test ore for value" , "Test gold" , "Analyse to find the properties" , "Test of substance" .)