Checks for suitability of American ex-servicemen (4)
I believe the answer is:
vets
This might be a double definition.
'checks' is the first definition.
(I've seen this in another clue)
'suitability of american ex-servicemen' is the second definition.
'vets' can be an answer for 'ex-servicemen' ('vet' can be a synonym of 'ex-serviceman'). I am not certain of the 'suitability of american' bit.
'for' is the link.
Can you help me to learn more?
(Other definitions for vets that I've seen before include "Investigates thoroughly to ensure suitability, for a job perhaps" , "Examines the animal doctors carefully?" , "Screens for the job perhaps" , "old soldiers" , "Inspects (animals?)" .)