Pulse from bachelor, say, began after heart bypass (10)

'heart bypass' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.

'pulse from bachelor say began' is the wordplay.
I cannot really see how this works, but
'pulse' could be 'bean' (beans are a type of pulse) and 'bean' is found within the answer.
'bachelor' could be 'b' (abbreviation e.g. BA=Bachelor of Arts) and 'b' is found in the answer.
'say' could be 'utter' (to utter something is to speak or say it) and 'utter' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...

'after' acts as a link.

Can you help me to learn more?