Begs forgiveness for what Alsatian in the security business is looking for (10)
I believe the answer is:
trespasser
'for' is the definition.
Both the answer and definition are singular nouns.
Perhaps they are linked in a way I don't understand?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for trespasser that I've seen before include "One entering land without permission" , "sinner" , "Intruder into another's land" , "Misplaced individual" , "One unlawfully entering another's land" .)