Imagined collapsed veins before one got older (9)
I believe the answer is:
envisaged
'imagined' is the definition.
('envisage' can be a synonym of 'imagine')
'collapsed veins before one got older' is the wordplay.
'collapsed' indicates anagramming the letters.
'before' means one lot of letters go next to another.
'one got older' becomes 'aged' (I've seen this before).
'veins' is an anagram of 'envis'.
'envis'+'aged'='ENVISAGED'
(Other definitions for envisaged that I've seen before include "Contemplated" , "Fancied" , "Pictured" , "anticipated" , "Imagined" .)