Setting up dinner support (8)
I believe the answer is:
underpin
'support' is the definition.
(I know that support can be written as underpin)
'setting up dinner' is the wordplay.
'setting' is an anagram indicator.
'up'+'dinner'='updinner'
'updinner' is an anagram of 'UNDERPIN'.
(Other definitions for underpin that I've seen before include "Prop up with nun pride" , "Support or strengthen from beneath" , "Form the basis for" , "buttress" , "corroborate" .)