A gaunt marshal outside institute - the one from the Leeward Islands (7)
I believe the answer is:
antigua
'islands' is the definition.
(I know that Antigua is a islands)
'a gaunt marshal outside institute the one' is the wordplay.
'marshal' is an anagram indicator (I've seen 'marshals' mean this (marshal can mean to gather)).
'outside' indicates putting letters inside.
'institute' becomes 'i' (common abbreviation as in MIT).
'the one' becomes 'a' (a thing is one thing).
'gaunt' anagrammed gives 'antgu'.
'antgu' going around 'i' is 'antigu'.
'antigu'+'a'='ANTIGUA'
'from the leeward' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for antigua that I've seen before include "holiday destination" , "Caribbean island linked with Barbuda" , "One of the Leeward Islands" , "West Indies island" , "warm island" .)