We are amongst the old, decrepit and let down (7)
I believe the answer is:
lowered
'let down' is the definition.
(I've seen this in another clue)
'we are amongst the old decrepit' is the wordplay.
'we are' becomes 'we're' (contraction of 'we are').
'amongst' means one lot of letters goes inside another (I've seen this in other clues).
'decrepit' is an anagram indicator.
'old' is an anagram of 'lod'.
'were' placed within 'lod' is 'LOWERED'.
'and' acts as a link.
(Other definitions for lowered that I've seen before include "looked sullen" , "Moved something down" , "Let down gently" , "Moved downwards" , "Brought down" .)