Shift working interrupted by large strike (8)
I believe the answer is:
bludgeon
'strike' is the definition.
(thesaurus)
'shift working interrupted by large' is the wordplay.
'shift' becomes 'budge' (synonyms).
'working' becomes 'on' (on can mean working or activated).
'interrupted by' indicates putting letters inside.
'large' becomes 'L' (eg in clothes sizes).
'budge'+'on'='budgeon'
'budgeon' going around 'l' is 'BLUDGEON'.
(Other definitions for bludgeon that I've seen before include "Club used as a weapon" , "Beat repeatedly with a heavy object" , "(Beat with a) heavy stick" , "Bully; heavy weapon" , "Strike with a club" .)