Exercise expected to captivate eager teacher (9)
I believe the answer is:
pedagogue
'teacher' is the definition.
(I've seen this before)
'exercise expected to captivate eager' is the wordplay.
'exercise' becomes 'pe' (Physical Education).
'expected' becomes 'due' (similar in meaning).
'to captivate' is an insertion indicator.
'eager' becomes 'agog' (I've seen this before).
'due' placed around 'agog' is 'dagogue'.
'pe'+'dagogue'='PEDAGOGUE'
(Other definitions for pedagogue that I've seen before include "Strict teacher" , "Educator of young people" , "Dogmatic teacher" , "Schoolmaster" .)