Writer abandoned by the Spanish coalition (4)
I believe the answer is:
bloc
'coalition' is the definition.
(I know that bloc is a type of coalition)
'writer abandoned by the spanish' is the wordplay.
'writer' becomes 'belloc' (French writer Hilaire Belloc).
'abandoned by' is a deletion indicator.
'the spanish' becomes 'el' ('the' in Spanish).
'belloc' with 'el' removed is 'BLOC'.
(Other definitions for bloc that I've seen before include "Association of countries" , "Group of parties or countries united in common interest - sounds wooden" , "Political or economic confederation" , "Combination of nations" , "Political allies" .)