Missing worker rings bosses from time to time (6)
I believe the answer is:
absent
'missing' is the definition.
(similar in meaning)
'worker rings bosses from time to time' is the wordplay.
'worker' becomes 'ant' (worker is a type of ant).
'rings' means one lot of letters goes inside another.
'from time to time' indicates alternate letters (letters removed on a regular basis).
The alternating letters of 'bosses' are 'bse'.
'ant' going around 'bse' is 'ABSENT'.
(Other definitions for absent that I've seen before include "Forgetful, with mind on other things" , "Missing, lacking" , "Missing or dreamy" , "Not attending" , "elsewhere" .)