Country clubs supporting mostly environmentally friendly energy (6)
I believe the answer is:
greece
'country' is the definition.
(Greece is an example)
'clubs supporting mostly environmentally friendly energy' is the wordplay.
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'mostly' means to remove the last letter.
'environmentally friendly' becomes 'green' (I've seen this before).
'energy' becomes 'e' (physics symbol as in E=mc2).
'green' with its last letter taken away is 'gree'.
'c' put after 'gree' is 'greec'.
'greec'+'e'='GREECE'
(Other definitions for greece that I've seen before include "Country of southeast Europe" , "European nation" , "Country of Hellenes" , "EU country" , "Zorba's land" .)