Nobleman exercises with the Queen (4)
I believe the answer is:
peer
'nobleman' is the definition.
(peer is a kind of nobleman)
'exercises with the queen' is the wordplay.
'exercises' becomes 'pe' (Physical Education class).
'with' is a charade indicator (letters next to each other).
'the queen' becomes 'er' (abbreviation for Elizabeth Regina).
'pe'+'er'='PEER'
(Other definitions for peer that I've seen before include "Noble; look with difficulty" , "Equal -- look searchingly" , "Look hard through narrowed eyes" , "Gaze" , "Equal - match" .)