Got to the bottom of friend having no stomach to hold party (8)
I believe the answer is:
fathomed
'got to the bottom of' is the definition.
(to fathom is to measure the depth of something)
'friend having no stomach to hold party' is the wordplay.
'having no stomach' means to remove the middle letters (the inside or stomach of the word is removed).
'to hold' indicates putting letters inside.
'party' becomes 'athome' (historical term for a party or visiting period).
'friend' with its centre removed is 'fd'.
'fd' going around 'athome' is 'FATHOMED'.
(Other definitions for fathomed that I've seen before include "Sounded" , "Deeply understood" , "Got" .)