Clubs welcome letter from Greece (3)
I believe the answer is:
chi
'letter from greece' is the definition.
(letter from the Greek alphabet)
'clubs welcome' is the wordplay.
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'welcome' becomes 'hi' (I've seen this in other clues).
'c'+'hi'='CHI'
(Other definitions for chi that I've seen before include "Classical character" , "Greek character" , "Greek letter; Chinese life force" , "Chinese life-force" , "The life force, according to traditional Chinese medicine" .)