Old, initially sad story (5)
I believe the answer is:
stale
'old' is the definition.
(associated in meaning)
'initially sad story' is the wordplay.
'initially' indicates taking the first letters.
'story' becomes 'tale' (synonyms).
The first letter of 'sad' is 's'.
's'+'tale'='STALE'
(Other definitions for stale that I've seen before include "Old; musty" , "Mouldy or hackneyed" , "Boring" , "No longer take" , "Musty - out of date" .)