Walker greeting king and queen (5)
I believe the answer is:
hiker
'walker' is the definition.
(hiker is a kind of walker)
'greeting king and queen' is the wordplay.
'greeting' becomes 'hi' (hi is a kind of greeting).
'king' becomes 'k' (**).
'and' means one lot of letters go next to another.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'hi'+'k'+'er'='HIKER'
(Other definitions for hiker that I've seen before include "I could be on the trail" , "Person on walkabout" , "Long-distance walker" , "One on a walking tour" , "Someone who goes on an extended walk for pleasure" .)