Missing the old days tons, Gila moved back to suburbia (9)
I believe the answer is:
nostalgia
'missing the old days' is the definition.
I can't tell whether this defines the answer.
'tons gila moved back to suburbia' is the wordplay.
'moved' is an anagram indicator.
'back to' says to take the final letters.
The final letter of 'suburbia' is 'a'.
'tons'+'gila'='tonsgila'
'tonsgila' with letters rearranged gives 'nostalgi'.
'nostalgi'+'a'='NOSTALGIA'
Can you help me to learn more?
(Other definitions for nostalgia that I've seen before include "Wistful remembrance of analogist" , "longing for home and family" , "Backward-looking sentiment" , "Sense of past perfect" , "dreaming of the past" .)