Menial worker follows lad smuggling diamonds (8)
I believe the answer is:
dogsbody
'menial worker' is the definition.
(I've seen this before)
'follows lad smuggling diamonds' is the wordplay.
'follows' becomes 'dogs'.
'lad' becomes 'boy' (I've seen this before).
'smuggling' is an insertion indicator (I've seen this in other clues).
'diamonds' becomes 'd' (abbreviation in bridge say).
'boy' going around 'd' is 'body'.
'dogs'+'body'='DOGSBODY'
(Other definitions for dogsbody that I've seen before include "One who carries out menial tasks for another" , "One given menial tasks" , "Person doing menial jobs" , "Put-upon person" , "Flunkey" .)