Topless trespasser is high-value target (5)
I believe the answer is:
inner
'target' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for inner that I've seen before include "Located inside" , "Exclusive to a center" , "Good shot at archery" , "Opposite of outer" , "Deep" .)