Time to stop queen being keen (5)
I believe the answer is:
eager
'keen' is the definition.
(thesaurus)
'time to stop queen' is the wordplay.
'time' becomes 'age' (age is a kind of time).
'to stop' is an insertion indicator.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'age' going within 'er' is 'EAGER'.
'being' is the link.
(Other definitions for eager that I've seen before include "Sharp" , "Longing to see" , "Enthusiastic, agog" , "hungry" , "Keen - enthusiastic" .)