Battle was cut short by resistance (3)
I believe the answer is:
war
'battle' is the definition.
(I've seen this before)
'was cut short by resistance' is the wordplay.
'cut short' means to remove the last letter.
'by' says to put letters next to each other.
'resistance' becomes 'r' (abbreviation).
'was' with its final letter removed is 'wa'.
'wa'+'r'='WAR'
(Other definitions for war that I've seen before include "State of armed struggle" , "Period of hostilities" , "Strife" , "Sustained conflict" , "Open hostility" .)