After that, engineers become genuine (7)
I believe the answer is:
sincere
'genuine' is the definition.
(sincere can mean authentic or genuine)
'after that engineers' is the wordplay.
'after' becomes 'since' (since can mean from a certain time onwards).
'that engineers' becomes 're' (Royal Engineers).
'since'+'re'='SINCERE'
'become' is the link.
(Other definitions for sincere that I've seen before include "devout" , "Unaffected" , "Open and genuine, not deceitful" , "Honest, frank" , "Candid" .)