Girl and boy failing to start — editor cross (7)
I believe the answer is:
annoyed
'cross' is the definition.
(thesaurus)
'girl and boy failing to start editor' is the wordplay.
'girl' becomes 'ann' (**).
'and' means one lot of letters go next to another.
'failing to start' means to remove the first letter.
'editor' becomes 'ed'.
'boy' with its initial letter taken off is 'oy'.
'ann'+'oy'+'ed'='ANNOYED'
(Other definitions for annoyed that I've seen before include "put out" , "'Harassed, pestered (7)'" , "'Irritated, impatient (7)'" , "Displeased" , "Irritated, peeved" .)