Novice's knight trapped between king and queen (7)
I believe the answer is:
learner
'novice's' is the definition.
(learner is a kind of novice)
'knight trapped between king and queen' is the wordplay.
'knight' becomes 'n' (chess abbreviation).
'trapped between' indicates putting letters inside.
'king' becomes 'lear' (Shakespeare's King Lear).
'and' says to put letters next to each other.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'lear'+'er'='learer'
'n' inserted inside 'learer' is 'LEARNER'.
(Other definitions for learner that I've seen before include "Amateur" , "One gaining knowledge" , "A student or beginner" , "Trainee (driver)" , "One under instruction" .)