Grassland in southeast provides cover (7)
I believe the answer is:
sheathe
'cover' is the definition.
(to sheathe something is to cover it)
'grassland in southeast' is the wordplay.
'grassland' becomes 'heath' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'southeast' becomes 'SE' (synonyms).
'heath' inserted within 'se' is 'SHEATHE'.
'provides' is the link.
Can you help me to learn more?
(Other definitions for sheathe that I've seen before include "Encase in protection" , "Cover in case" , "Protective cover, for sword say" , "Put into scabbard" , "Put (a sword) into case" .)