Succeeding generations notice that thing on end of chimney (9)
I believe the answer is:
posterity
'succeeding generations' is the definition.
(I've seen this before)
'notice that thing on end of chimney' is the wordplay.
'notice' becomes 'poster' ('poster' can be a synonym of 'notice'**).
'that thing' becomes 'it'.
'on' is a charade indicator (letters next to each other).
'end of' indicates one should take the final letters.
The last letter of 'chimney' is 'y'.
'poster'+'it'+'y'='POSTERITY'
(Other definitions for posterity that I've seen before include "Succeeding generations" , "Future generations" , "for people coming later" .)