You heading back to lake and grassland (3)
I believe the answer is:
ley
'grassland' is the definition.
(I know that ley is a type of grassland)
'you heading back to lake' is the wordplay.
'you' becomes 'ye' (historical version of 'you').
'heading back' is a reversal indicator.
'to' means one lot of letters go next to another (I've seen this in other clues).
'lake' becomes 'L' (geographical abbreviation).
'ye' backwards is 'ey'.
'ey' put after 'l' is 'LEY'.
'and' acts as a link.
(Other definitions for ley that I've seen before include "Supposed line connecting ancient sites" , "Field; straight track" , "Supposed ancient straight track" , "Arable land under grass" .)