Sorry a girl's lost, that is (3)
I believe the answer is:
sad
'sorry a girl's lost that is' is the definition.
'sad' can be an answer for 'sorry' (I've seen this before). I am not certain of the remainder of the definition.
'sorry a girl's lost' is the wordplay.
'sorry' indicates an anagram (letters in a sorry state).
'girl's' becomes 'ada's' (girl's name).
'lost' suggests deleting specific letters.
'adas' with 'a' taken away is 'das'.
'das' with letters rearranged gives 'SAD'.
Can you help me to learn more?
(Other definitions for sad that I've seen before include "grey" , "Despondent" , "Dejected" , "Deplorable" , "Doleful" .)