They say you ultimately finish in incontinence pad, being miserable (7)
I believe the answer is:
unhappy
'miserable' is the definition.
(similar in meaning)
'they say you ultimately finish in incontinence pad' is the wordplay.
'they say' indicates a 'sounds like' (homophone) clue.
'ultimately' indicates one should take the final letters.
'in' indicates putting letters inside.
'incontinence pad' becomes 'nappy'.
The last letter of 'finish' is 'h'.
'you' is a homophone of 'u'.
'h' placed into 'nappy' is 'nhappy'.
'u'+'nhappy'='UNHAPPY'
'being' is the link.
(Other definitions for unhappy that I've seen before include "Sad, distressed" , "Not contented or peaceful" , "Sad, miserable" , "Dejected, not contented" , "Unfortunate; miserable" .)