Cycle stocked by old worker is a rip-off (10)
I believe the answer is:
exorbitant
'is a rip-off' is the definition.
'cycle stocked by old worker' is the wordplay.
'cycle' becomes 'orbit'.
'stocked by' is an insertion indicator.
'old' becomes 'ex'.
'worker' becomes 'ant' (worker is a type of ant).
'ex'+'ant'='exant'
'orbit' placed into 'exant' is 'EXORBITANT'.
(Other definitions for exorbitant that I've seen before include "Exceeding the bounds of reason" , "Very dear" , "High cost" , "Unreasonable" , "going beyond the limits?" .)