Sick men admitted into educational institution (6)
I believe the answer is:
poorly
'sick' is the definition.
(similar in meaning)
'men admitted into educational institution' is the wordplay.
I cannot really understand how this works, but
'men' could be 'or' (military abbreviation for Other Ranks) and 'or' is located in the answer.
The remaining letters 'poly' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for poorly that I've seen before include "Feeling unwell - or broke?" , "sick" , "Unhealthy" , "Being unwell or deficient" , "Out of sorts" .)