Some treasure trove appearing from the past (5)
I believe the answer is:
retro
'from the past' is the definition.
'some treasure trove appearing' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'RETRO' is hidden in the letters of 'treasure trove appearing'.
(Other definitions for retro that I've seen before include "Predatory fish" , "sort of rocket" , "Type of rocket; backward-looking" , "Slangy adjective for harking back to the past" , "recreating the past for effect" .)