Become engaged in some sharp practice (4)
I believe the answer is:
mesh
'become engaged' is the definition.
(I've seen this before)
'in some sharp practice' is the wordplay.
'in' indicates the answer is hidden within the clue.
'MESH' is hidden in the letters of 'some sharp practice'.
(Other definitions for mesh that I've seen before include "Interconnected configuration" , "Work well together" , "Network fabric - engage with it" , "Net fabric" , "Grid, netting" .)