Twelvemonth (4)
I believe the answer is:
year
'twelvemonth' is the definition.
(I know that twelvemonth can be written as year)
This is the entire clue.
(Other definitions for year that I've seen before include "See 33 Across" , "1% of a century" , "12 months" , "See 9" , "26 fortnights" .)