Atmosphere created by girl heading off (4)
I believe the answer is:
aura
'atmosphere' is the definition.
(synonyms)
'girl heading off' is the wordplay.
'girl' becomes 'Laura' (girl's name).
'heading off' means to remove the first letter.
'laura' with its first letter taken off is 'AURA'.
'created by' is the link.
(Other definitions for aura that I've seen before include "Distinctive quality around a person or place" , "Intangible air or quality" , "Particular ambience" , "Distinctive but intangible quality surrounding a person" , "Intangible essence emanating from a person" .)