Manager's fantastic eyeshade (10)
I believe the answer is:
supervisor
'manager's' is the definition.
(I've seen this before)
'fantastic eyeshade' is the wordplay.
'fantastic' becomes 'super' (I've seen this in another clue).
'eyeshade' becomes 'visor' (synonyms).
'super'+'visor'='SUPERVISOR'
(Other definitions for supervisor that I've seen before include "Man in charge" , "One looks over" , "gaffer?" , "Line manager" , "Tutor" .)