Sensible person - the others have a large one (7)
I believe the answer is:
realist
'sensible' is the definition.
(thesaurus)
'others have a large one' is the wordplay.
'others' becomes 'rest' (eg the rest of a group).
'have' means one lot of letters goes inside another.
'large' becomes 'L' (eg in clothes sizes).
'one' becomes 'i' (Roman numeral).
'a'+'l'+'i'='ali'
'rest' going around 'ali' is 'REALIST'.
'person the' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for realist that I've seen before include "Pragmatist" , "Retails like practical person" , "Is alert (anag)" , "no Walter Mitty?" , "One with a pragmatic attitude" .)