Neat edge on front of topiary (4)
I believe the answer is:
trim
'neat' is the definition.
('trim' can be a synonym of 'neat')
'edge on front of topiary' is the wordplay.
'edge' becomes 'rim' (rim is a kind of edge).
'on' says to put letters next to each other.
'front of' indicates taking the first letters.
The first letter of 'topiary' is 't'.
'rim' put after 't' is 'TRIM'.
(Other definitions for trim that I've seen before include "Reduce slightly" , "To change views expediently" , "Cut, prune; decorate" , "Dress - prune" , "(Make) neat and tidy" .)