Portion of salary earned for a time (4)
I believe the answer is:
year
'a time' is the definition.
(I've seen this before)
'portion of salary earned for' is the wordplay.
'portion of' says the answer is hidden in the clue.
'YEAR' can be found hidden inside 'salary earned for'.
(Other definitions for year that I've seen before include "Division of school" , "1381 say" , "Time taken by a planet to orbit the sun" , "One tenth of a decade" , "Period of just over 52 weeks" .)