Unhappy exhausted delegate carrying large burden (6)
I believe the answer is:
saddle
'burden' is the definition.
(I know that saddle is a kind of burden)
'unhappy exhausted delegate carrying large' is the wordplay.
'unhappy' becomes 'sad' (associated in meaning).
'exhausted' says to hollow out the word (remove centre letters) (the word is emptied out or exhausted).
'carrying' is an insertion indicator.
'large' becomes 'L' (eg in clothes sizes).
'delegate' with its middle removed is 'de'.
'de' placed around 'l' is 'dle'.
'sad'+'dle'='SADDLE'
(Other definitions for saddle that I've seen before include "Seat for riding" , "Seat for a rider, horse or bike" , "Impose a task on -- assign responsibility for" , "Encumber" , "Cut of meat" .)