Model retirement payment doesn’t start... results in stress (7)
I believe the answer is:
tension
'stress' is the definition.
(synonyms)
'model retirement payment doesn't start' is the wordplay.
'model' becomes 't' (Ford Model T car).
'retirement payment' becomes 'pension' (I've seen this before).
'doesn't start' means to remove the first letter.
'pension' with its first letter taken away is 'ension'.
't'+'ension'='TENSION'
'results in' is the link.
(Other definitions for tension that I've seen before include "anxious state" , "State of strain or suspense" , "Intones (anag) - stress" , "Strained condition" , "The effect of force exerted in or on something" .)