They may learn to operate as groups of three (7)
I believe the answer is:
interns
'they' is the definition.
Both the definition and answer are plural nouns.
Maybe you can see an association between them that I don't see?
'learn to operate as groups of three' is the wordplay.
I cannot really see how this works, but
'three' could be 'ter' (see Chambers) and 'ter' is found in the answer.
The remaining letters 'inns' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'may' acts as a link.
Can you help me to learn more?
(Other definitions for interns that I've seen before include "Hospital residents" , "those confined" .)