Laments idea regularly adopted by European members (7)
I believe the answer is:
elegies
'laments' is the definition.
('elegy' can be a synonym of 'lament')
'idea regularly adopted by european members' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'adopted by' indicates putting letters inside (I've seen this in other clues).
'european' becomes 'e' (abbreviation e.g. EU).
'members' becomes 'legs' (leg is a kind of member**).
The alternating letters of 'idea' are 'ie'.
'e'+'legs'='elegs'
'ie' going within 'elegs' is 'ELEGIES'.
(Other definitions for elegies that I've seen before include "Poems of mourning" , "Lamenting poems" , "Mourning songs" , "Laments for the dead" .)