Expose oneself illegally to plague local English spiv (5,5)
I believe the answer is:
flash harry
'spiv' is the definition.
(I've seen this before)
'expose oneself' is the wordplay.
'expose' becomes 'flash' (flashing is a kind of exposing).
'oneself' becomes 'harry' (I can't explain this - if you can you should believe this answer much more).
'flash'+'harry'='FLASH HARRY'
'illegally to plague local english' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for flash harry that I've seen before include "Spiv" , "one likes to show off" , "Show-off" , "wide boy" , "Vulgar type" .)