Good to leave the upper class no way out (5)
I believe the answer is:
entry
'no way out' is the definition.
(an entry is a way in)
'good to leave the upper class' is the wordplay.
'good' becomes 'g' (abbreviation).
'to leave' suggests deleting specific letters.
'the upper class' becomes 'gentry' (gentry is a kind of upper class).
'gentry' with 'g' taken away is 'ENTRY'.
(Other definitions for entry that I've seen before include "List of candidates" , "Gate" , "Admittance" , "Door, access" , "all runners" .)