Wrote, oddly, to plead with person, being miserable (9)
I believe the answer is:
woebegone
'miserable' is the definition.
(thesaurus)
'wrote oddly to plead with person' is the wordplay.
'oddly' means one should take alternating letters (letters in the odd-numbered positions are used).
'to plead with' becomes 'beg' (I've seen this in another clue).
'person' becomes 'one' ('one' can mean an unspecified person).
The alternate letters of 'wrote' are 'woe'.
'woe'+'beg'+'one'='WOEBEGONE'
'being' acts as a link.
(Other definitions for woebegone that I've seen before include "Miserable-looking" , "Sad, miserable" , "Miserable in appearance" , "crestfallen" , "Looking sad" .)