Spain alerted to change after last month and slowed down (11)
I believe the answer is:
decelerated
'slowed down' is the definition.
('decelerate' can be a synonym of 'slow down')
'spain alerted to change after last month' is the wordplay.
'spain' becomes 'e' (abbreviation for Espana).
'to change' indicates an anagram.
'after' means one lot of letters go next to another.
'last month' becomes 'dec'.
'alerted' anagrammed gives 'lerated'.
'e'+'lerated'='elerated'
'elerated' after 'dec' is 'DECELERATED'.
'and' acts as a link.
(Another definition for decelerated that I've seen is " Slowed down".)