Went to protect my back in advance (7)
I believe the answer is:
proceed
'advance' is the definition.
(I've seen this in another clue)
'went to protect my back' is the wordplay.
'went' becomes 'peed' (both can mean urinated).
'to protect' indicates putting letters inside.
'my' becomes 'cor' (both are expressions of surprise).
'back' says the letters should be written in reverse.
'cor' back-to-front is 'roc'.
'peed' placed around 'roc' is 'PROCEED'.
'in' is the link.
(Other definitions for proceed that I've seen before include "Go forward" , "'Continue, move ahead (7)'" , "Continue, carry on" , "Move forward" , "Continue, go ahead" .)