Lucky mascot of Dutch explorer crossing large island (8)
I believe the answer is:
talisman
'lucky mascot' is the definition.
'dutch explorer crossing large island' is the wordplay.
'dutch explorer' becomes 'tasman' (17th-century explorer Abel Tasman).
'crossing' means one lot of letters goes inside another.
'large' becomes 'l'.
'island' becomes 'i'.
'l'+'i'='li'
'tasman' going around 'li' is 'TALISMAN'.
'of' acts as a link.
(Other definitions for talisman that I've seen before include "Amulet" , "bringer of luck?" , "Mascot" , "which is charming" , "Object supposed to guard against evil" .)