Former queen has time to make an effort (5)
I believe the answer is:
exert
'make an effort' is the definition.
(exerting oneself by making a special effort)
'former queen has time' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'has' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'ex'+'er'+'t'='EXERT'
'to' is the link.
(Other definitions for exert that I've seen before include "Make use of" , "Put to use, vigorously" , "Bring into play, wield" , "Wield - apply" , "Bring to bear, perhaps influence" .)