Second catering worker I sacked in isolated location (9)
I believe the answer is:
backwater
'isolated location' is the definition.
(backwater can mean an isolated place)
'second catering worker i sacked in' is the wordplay.
'second' becomes 'back' (to second a motion is to back it).
'catering worker' becomes 'waiter' (someone who provides food).
'sacked in' suggests deleting specific letters (sack can mean to remove or dismiss).
'waiter' with 'i' taken out is 'water'.
'back'+'water'='BACKWATER'
(Other definitions for backwater that I've seen before include "in the sticks" , "place of inactivity" , "Place where no development happens" , "Stagnant part of a river" , "Isolated spot" .)