Diminish and place Spanish article the other way (3,2)
I believe the answer is:
let up
'diminish' is the definition.
(I know that let up is a more specific form of the action diminish)
'place spanish article the other way' is the wordplay.
'place' becomes 'put' (synonyms).
'spanish article' becomes 'el' (the definite article 'the' in Spanish).
'the other way' is a reversal indicator.
'put'+'el'='putel'
'putel' back-to-front is 'LET-UP'.
'and' acts as a link.
(Other definitions for let up that I've seen before include "Alleviate" , "Abate" , "Slack off" , "Slackening" , "Die away, ease off" .)