Corpulent friend followed with deadly result (7)
I believe the answer is:
fatally
'corpulent friend followed with deadly result' is the definition.
I can't tell whether this definition defines the answer.
'corpulent friend followed' is the wordplay.
'corpulent' becomes 'fat' (similar in meaning).
'friend' becomes 'ally' (an ally is a friend or supporter).
'followed' means one lot of letters go next to another.
'fat'+'ally'='FATALLY'
Can you help me to learn more?
(Other definitions for fatally that I've seen before include "So as to cause death" , "in decisive manner" , "Mortally" , "with no hope of revival" , "producing disastrous result" .)