Bacteriologist's gone his own way in retirement (7)
I believe the answer is:
pasteur
'bacteriologist's' is the definition.
(I've seen this before)
'own way in retirement' is the wordplay.
'own' becomes 'past' (I can't justify this - if you can you should give a lot more credence to this answer).
'way' becomes 'rue' (I have seen 'French way' mean 'rue' so perhaps 'way' could also mean 'rue').
'in retirement' is a reversal indicator (retire can mean to go back or backwards).
'rue' backwards is 'eur'.
'past'+'eur'='PASTEUR'
'gone his' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for pasteur that I've seen before include "Famous bacteriologist" , "French chemist, 1822-95" , "French chemist and biologist, d. 1895" , "Louis --, French chemist and microbiologist" , "He invented a method to stop milk causing disease" .)