I resume training with Hewett, finally, having retained title (8)
I believe the answer is:
emeritus
'retained title' is the definition.
(I've seen this before)
'i resume training with hewett finally' is the wordplay.
'training with' is an anagram indicator (to train can mean to grow something into a shape).
'finally' suggests the final letters.
The last letter of 'hewett' is 't'.
'i'+'resume'='iresume'
'iresume' with its letters mixed up with 't' makes 'EMERITUS'.
'having' acts as a link.
(Other definitions for emeritus that I've seen before include "Title given to retired professor" , "Designation of retired person" , "Retired, but retaining the title of one's office" , "Professor honourably retired" , "Honorary title" .)