Covering part of lawn in garden (6)
I believe the answer is:
awning
'covering' is the definition.
(awning is a kind of covering)
'part of lawn in garden' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'AWNING' can be found hidden inside 'lawn in garden'.
(Other definitions for awning that I've seen before include "Canvas sunshield" , "Shop front cover" , "It keeps sun and rain off a shop window" , "Protection" , "Shade over shop window" .)