Souvenir from Long Island found in park (5)
I believe the answer is:
relic
'souvenir' is the definition.
('relic' can be a synonym of 'souvenir')
'long island found in park' is the wordplay.
'long' becomes 'l'.
'island' becomes 'i'.
'found in' means one lot of letters goes inside another.
'park' becomes 'rec' (I've seen this in other clues).
'l'+'i'='li'
'li' placed inside 'rec' is 'RELIC'.
'from' is the link.
(Other definitions for relic that I've seen before include "Revered holy item" , "E,g. dead saint's bone" , "Reminder of times past" , "an old fogey..." , "(Holy) remains" .)