Clapped-out drier beginning to erode on the bottom (8)
I believe the answer is:
derriere
'the bottom' is the definition.
('derriere' can be a synonym of 'bottom')
'clapped-out drier beginning to erode on' is the wordplay.
'clapped-out' indicates anagramming the letters.
'beginning to' indicates taking the first letters.
'on' becomes 're' ('on' can be mean 'with reference to'**).
The first letter of 'erode' is 'e'.
'drier' is an anagram of 'derri'.
'derri'+'e'+'re'='DERRIERE'
(Other definitions for derriere that I've seen before include "Seat" , "Fourteen down's [FRENCHMAN] behind" , "(French?) behind" , "A French backside or buttocks" , "One's backside in France" .)