Half-decent Queen record (5)
I believe the answer is:
enter
'record' is the definition.
('enter' can be a synonym of 'record')
'half-decent queen' is the wordplay.
'half' indicates taking half.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'decent' halved is 'ent'.
'ent'+'er'='ENTER'
(Other definitions for enter that I've seen before include "Inscribe" , "Set foot in" , "Enlist, join up" , "Record - stage direction - come in" , "Make a record of" .)