Allegiance from 50 kings and queens? Not at first (7)
I believe the answer is:
loyalty
'allegiance' is the definition.
(thesaurus)
'50 kings and queens? not at first' is the wordplay.
'50' becomes 'l' ('L' can be a synonym of '50').
'kings and queens?' becomes 'royalty'.
'not at first' means to remove the first letter.
'royalty' with its initial letter taken away is 'oyalty'.
'l'+'oyalty'='LOYALTY'
'from' is the link.
(Other definitions for loyalty that I've seen before include "Fidelity, allegiance" , "Firm allegiance" , "Strong allegiance" , "Alligiance and fidelity" , "Allegiance, commitment" .)