Author in the end opens pink pen (6)
I believe the answer is:
corral
'pen' is the definition.
(both are a type of enclosure for animals)
'author in the end opens pink' is the wordplay.
'in the end' says to take the final letters.
'opens' means one lot of letters goes inside another (one set of letters makes an 'opening' in another).
'pink' becomes 'coral' (coral is a shade of pink).
The last letter of 'author' is 'r'.
'r' going into 'coral' is 'CORRAL'.
(Other definitions for corral that I've seen before include "Round up" , "Pen for cattle - ring of waggons" , "American enclosure for horses" , "Pen for livestock (US)" , "Ranch pen" .)