Constant European learnt in new form (7)
I believe the answer is:
eternal
'constant' is the definition.
(I've seen this before)
'european learnt in new form' is the wordplay.
'european' becomes 'e' (abbreviation e.g. EU).
'in new form' indicates an anagram.
'learnt' with letters rearranged gives 'ternal'.
'e'+'ternal'='ETERNAL'
(Other definitions for eternal that I've seen before include "carrying on endlessly" , "'Lasting forever, unending (7)'" , "non-stop" , "Continuing forever or indefinitely" , "with lasting benefit" .)