Being sacked go back for some support (7)
I believe the answer is:
firedog
'for some support' is the definition.
(firedog is a kind of support)
'being sacked go back' is the wordplay.
'being sacked' becomes 'fired' (both can mean dismissed from a job).
'back' shows that the letters should be reversed in order.
'go' backwards is 'og'.
'fired'+'og'='FIREDOG'
(Other definitions for firedog that I've seen before include "hearth fixture" , "Andiron" , "support for logs" , "Hearth support" , "Enthuse boxer, say" .)