Got better chief to hold the Spanish back (6)
I believe the answer is:
healed
'got better' is the definition.
('heal' can be a synonym of 'get better')
'chief to hold the spanish back' is the wordplay.
'chief' becomes 'head' (synonyms).
'to hold' is an insertion indicator.
'the spanish' becomes 'el' ('the' in Spanish).
'back' is a reversal indicator.
'el' in reverse letter order is 'le'.
'head' enclosing 'le' is 'HEALED'.
(Other definitions for healed that I've seen before include "Cured, mended" , "Mended, recovered" , "Became well again" , "Put right" , "Made well" .)