The Spanish moan, upset and weak (6)
I believe the answer is:
feeble
'weak' is the definition.
(similar in meaning)
'the spanish moan upset' is the wordplay.
'the spanish' becomes 'el'.
'moan' becomes 'beef' (both can informally mean a criticism).
'upset' says the letters should be written backwards.
'el'+'beef'='elbeef'
'elbeef' back-to-front is 'FEEBLE'.
'and' is the link.
(Other definitions for feeble that I've seen before include "rather weak" , "lacking resolve" , "Weak, lacking strength" , "Very weak, without strength" , "Weak, debilitated" .)