Attack with stone, roughly (5)
I believe the answer is:
onset
'attack' is the definition.
(archaic term for a military attack)
'stone roughly' is the wordplay.
'roughly' indicates an anagram.
'stone' anagrammed gives 'ONSET'.
'with' acts as a link.
(Other definitions for onset that I've seen before include "Advent" , "Inception" , "Start - attack" , "Attack using stone" , "Outbreak" .)