After onset of gangrene sailor lost blood and talked incoherently (7)
I believe the answer is:
Here is my best explanation:
'talked incoherently' is the definition.
'after onset of gangrene sailor lost blood' is the wordplay.
'after' is a charade indicator (letters next to each other).
'onset of' indicates taking the first letters.
'sailor' becomes 'ab' (abbreviation for able seaman).
'lost blood' becomes 'bled' (I've seen this before).
The initial letter of 'gangrene' is 'g'.
'g' next to 'ab' is 'gab'.
'and' is the link.