Hopelessly lost again in yearning for the past (9)
I believe the answer is:
nostalgia
'yearning for the past' is the definition.
(I've seen this in another clue)
'hopelessly lost again' is the wordplay.
'hopelessly' is an anagram indicator.
'lost'+'again'='lostagain'
'lostagain' with letters rearranged gives 'NOSTALGIA'.
'in' is the link.
(Other definitions for nostalgia that I've seen before include "Sentimental feeling of analogist" , "Love for the past" , "Longing for things past" , "Yearning for past - homesickness" , "Fond memories" .)