Arrives with a couple of letters (5)
I believe the answer is:
lands
'arrives' is the definition.
(landing is a kind of arriving)
'with a couple of letters' is the wordplay.
'with' means one lot of letters goes inside another.
'a' becomes 'an'.
'couple of letters' becomes 'lds' (I can't explain this - if you can you should believe this answer much more).
'an' inserted inside 'lds' is 'LANDS'.
Can you help me to learn more?
(Other definitions for lands that I've seen before include "Alights" , "Comes ashore" , "See 21" , "Obtains" .)