Send back the Spanish meat as inadequate (6)
I believe the answer is:
feeble
'inadequate' is the definition.
(I've seen this in another clue)
'send back the spanish meat' is the wordplay.
'send back' says the letters should be written in reverse.
'the spanish' becomes 'el' ('the' in Spanish).
'meat' becomes 'beef' (type of meet).
'el'+'beef'='elbeef'
'elbeef' back-to-front is 'FEEBLE'.
'as' acts as a link.
(Other definitions for feeble that I've seen before include "Very weak, infirm" , "rather weak" , "Weak or Fragile" , "Lacking force" , "lacking resolve" .)