More than half of dons exaggerate (6)
I believe the answer is:
overdo
'exaggerate' is the definition.
('overdo' can be a synonym of 'exaggerate')
'more than half of dons' is the wordplay.
'more than' becomes 'over' (I've seen this before).
'half of' suggests halving the letters.
'dons' halved is 'do'.
'over'+'do'='OVERDO'
(Other definitions for overdo that I've seen before include "Cook wrongly" , "Exaggerate; use too much of" , "Be excessive, say cook too long" , "Carry too far" , "Maybe burn" .)