Tearful, Charles, upset about my rejected love (10)
I believe the answer is:
lachrymose
'tearful' is the definition.
(I've seen this before)
'charles upset about my rejected love' is the wordplay.
'upset' indicates an anagram.
'about' is an insertion indicator.
'rejected' says the letters should be written backwards.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'my' in reverse letter order is 'ym'.
'charles' anagrammed gives 'lachrse'.
'ym'+'o'='ymo'
'lachrse' enclosing 'ymo' is 'LACHRYMOSE'.
(Other definitions for lachrymose that I've seen before include "showing sorrow" , "Tearful (literary)" , "Sad" , "In bits" , "Weepy" .)