Partner is getting changed to come out (9)
I believe the answer is:
transpire
'come out' is the definition.
(thesaurus)
'partner is getting changed' is the wordplay.
'getting' says to put letters next to each other.
'changed' is an anagram indicator.
'partner'+'is'='partneris'
'partneris' with letters rearranged gives 'TRANSPIRE'.
'to' acts as a link.
(Other definitions for transpire that I've seen before include "exhale" , "Terrapins (anag)" , "Turn out" , "Ensue with terrapins" , "Prove to be so, happen" .)