Glyndebourne company's trip putting off posh conductor? (8)
I believe the answer is:
operator
'conductor?' is the definition.
(someone performing a particular task)
'glyndebourne company's trip putting off posh' is the wordplay.
'glyndebourne company' becomes 'opera' (Glyndebourne is an opera house).
'trip' becomes 'tour' (a journey or expedition).
'putting off' indicates named letters should be taken away.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-U).
'tour' with 'u' removed is 'tor'.
'opera'+'tor'='OPERATOR'
(Other definitions for operator that I've seen before include "Mathematical symbol" , "Conductor" , "Driver" , "Switchboard employee" , "Person who controls machinery" .)