Quite rare, yet growing wild in former times (10)
I believe the answer is:
yesteryear
'in former times' is the definition.
(I've seen this before)
'quite rare yet growing wild' is the wordplay.
'quite' becomes 'yes' ('quite!' can be used to express agreement).
'growing wild' is an anagram indicator.
'rare'+'yet'='rareyet'
'rareyet' anagrammed gives 'teryear'.
'yes'+'teryear'='YESTERYEAR'
(Other definitions for yesteryear that I've seen before include "The recent past" , "Twelve months ago" , "Days gone by" , "Former times" , "Time disappeared" .)