Worried virago recognised half of them (8)
I believe the answer is:
agonised
'worried' is the definition.
(to agonise is to worry or fret)
'virago recognised half of them' is the wordplay.
I cannot really see how this works, but
'of' could be 'o' and 'o' is present in the answer.
'recognised' could be 'agnised' ('agnise' can be a synonym of 'recognize') and 'agnised' is located in the leftover letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for agonised that I've seen before include "Underwent mental anguish (over something)" , "Diagnose (anag)" , "Did Labour" , "Very pained" , "Tormented" .)