Look back over bridgehead, repeat and destroy (10)
I believe the answer is:
obliterate
'destroy' is the definition.
(thesaurus)
'look back over bridgehead repeat' is the wordplay.
'look' becomes 'lo'.
'back' says the letters should be written backwards.
'over' is an insertion indicator.
'bridgehead' becomes 'b' (head letter of 'bridge').
'repeat' becomes 'iterate' ('iterate' can be a synonym of 'repeat'**).
'lo' written backwards gives 'ol'.
'ol' going around 'b' is 'obl'.
'obl'+'iterate'='OBLITERATE'
'and' is the link.
(Other definitions for obliterate that I've seen before include "Erase" , "use eraser" , "Put an end to" , "Annihilate" , "Efface, blot out" .)