Being about to go in whole (8)
I believe the answer is:
entirety
'whole' is the definition.
(I've seen this before)
'being about to go' is the wordplay.
'being' becomes 'entity' (I've seen this in other clues).
'about' is an insertion indicator.
'to go' becomes 're' (I've seen this in other clues).
'entity' enclosing 're' is 'ENTIRETY'.
'in' is the link.
(Other definitions for entirety that I've seen before include "Absoluteness" , "Totality" , "Whole" , "Universe" , "Completeness" .)