Open country to warm the heart! (5)
I believe the answer is:
heath
'open country' is the definition.
(thesaurus)
'warm the heart' is the wordplay.
'warm' becomes 'heat'.
'heart' says to take the centre.
The middle letter of 'the' is 'h'.
'heat'+'h'='HEATH'
'to' acts as a link.
(Other definitions for heath that I've seen before include "Scrubland" , "Moorland shrub" , "Common land; ex-PM" , "Statesman" , "Sir Edward - , PM" .)