Bearing on a lever manipulated by a worker (8)
I believe the answer is:
relevant
'bearing on' is the definition.
(relevant can mean having a bearing on something)
'a lever manipulated by a worker' is the wordplay.
'manipulated' indicates anagramming the letters.
'by' says to put letters next to each other.
'a worker' becomes 'ant' (worker is a type of ant).
'lever' with letters rearranged gives 'relev'.
'relev'+'ant'='RELEVANT'
(Other definitions for relevant that I've seen before include "Applicable" , "Suitable" , "Bearing upon the matter in hand" , "Apt" , "Related to the matter in hand" .)