Officers in Spain act oddly (8)
I believe the answer is:
captains
'officers' is the definition.
(I know this)
'spain act oddly' is the wordplay.
'oddly' indicates anagramming the letters (letters in an odd order).
'spain'+'act'='spainact'
'spainact' is an anagram of 'CAPTAINS'.
'in' acts as a link.
(Other definitions for captains that I've seen before include "Leading men" , "Commanders of troops" , "Officers, in command of ships say (8)" , "Commissioned officers" , "Officers below major" .)