Work involving operations in part of garden (7)
I believe the answer is:
topsoil
'part of garden' is the definition.
'work involving operations' is the wordplay.
'work' becomes 'toil' (toiling is a kind of working**).
'involving' means one lot of letters goes inside another.
'operations' becomes 'ops' (I have seen 'Military operations ' mean 'ops' so perhaps 'operations' could also mean 'ops').
'toil' enclosing 'ops' is 'TOPSOIL'.
'in' is the link.
(Other definitions for topsoil that I've seen before include "Garden's surface layer" , "The Good Earth" , "surface of earth" , "best part of earth" , "Upper garden layer" .)