Reveal hesitation about nationalist question (6)
I believe the answer is:
unmask
'reveal' is the definition.
(I've seen this in another clue)
'hesitation about nationalist question' is the wordplay.
'hesitation' becomes 'um' (um is said in hesitation).
'about' is an insertion indicator.
'nationalist' becomes 'n' (abbreviation in politics).
'question' becomes 'ask' (asking a question).
'um' placed around 'n' is 'unm'.
'unm'+'ask'='UNMASK'
(Other definitions for unmask that I've seen before include "Disclose (the hidden nature of)" , "establish identity" , "Expose, remove face covering" , "Expose, remove cover" , "Identify (someone hidden)" .)