First of tenors leading Queen without end (8)
I believe the answer is:
terminus
'end' is the definition.
(terminus is a kind of end)
'first of tenors leading queen without' is the wordplay.
'first of' indicates taking the first letters.
'leading' says to put letters next to each other.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'without' becomes 'minus' (I've seen this before**).
The first letter of 'tenors' is 't'.
't'+'er'+'minus'='TERMINUS'
(Other definitions for terminus that I've seen before include "End station" , "End of the line, bus or train" , "Roman god of boundaries" , "Final stop" , "End of bus/rail route" .)