Inca gets hidden pen (4)
I believe the answer is:
cage
'pen' is the definition.
(thesaurus)
'inca gets hidden' is the wordplay.
'hidden' says the answer is hidden in the clue.
'CAGE' is hidden within 'inca gets'.
(Other definitions for cage that I've seen before include "Wired enclosure" , "US avant-garde composer, d. 1992" , "Enclose with bars" , "Hutch" , "American composer with centenary this year" .)