OK ... oddjobber taking year to become reliable type (5-4,3)
I believe the answer is:
right-hand man
'reliable type' is the definition.
'ok oddjobber taking year' is the wordplay.
'ok' becomes 'right' (I've seen this in other clues).
'oddjobber' becomes 'handy man'.
'taking' is a deletion indicator.
'year' becomes 'y'.
'handyman' with 'y' taken away is 'handman'.
'right'+'handman'='RIGHT-HAND MAN'
'to become' acts as a link.
(Other definitions for right-hand man that I've seen before include "Most trusted assistant" , "Indispensable personal aide" , "One's most valuable assistant" , "Reliable assistant" , "Indispensable assistant" .)