European lair -- delightful place! (4)
I believe the answer is:
eden
'delightful place' is the definition.
(I've seen this in another clue)
'european lair' is the wordplay.
'european' becomes 'e' (abbreviation e.g. EU).
'lair' becomes 'den' (synonyms).
'e'+'den'='EDEN'
(Other definitions for eden that I've seen before include "at Number Ten once?" , "PM, 1955-57" , "The first garden" , "prime minister in the past" , "Need an odd garden?" .)