Girl, no leader, creates atmosphere (4)
I believe the answer is:
aura
'atmosphere' is the definition.
(synonyms)
'girl no leader' is the wordplay.
'girl' becomes 'Laura' (girl's name).
'no leader' means to remove the first letter.
'laura' with its initial letter taken away is 'AURA'.
'creates' is the link.
(Other definitions for aura that I've seen before include "Distinctive but intangible quality surrounding a person" , "Distinctive character, essence of a living thing" , "Atmosphere, quality" , "Intangible something around a person" , "Intangible air or quality" .)