Old croupier eventually cut deck (5)
I believe the answer is:
orlop
'deck' is the definition.
(a deck on a ship)
'old croupier eventually cut' is the wordplay.
'old' becomes 'o' (abbreviation).
'eventually' says to take the final letters.
'cut' becomes 'lop' (lopping is a kind of cutting).
The final letter of 'croupier' is 'r'.
'o'+'r'+'lop'='ORLOP'
(Other definitions for orlop that I've seen before include "deck at the lowest point" , "Lowest deck of a wooden sailing ship" , "Ship's lowest deck" , "hold covering" , "part of ship" .)