It may guide a traveller around deserts (4)
I believe the answer is:
star
'it may guide a traveller' is the definition.
The definition suggests a singular noun which matches the answer.
'around deserts' is the wordplay.
'around' is a reversal indicator.
'deserts' becomes 'rats' (ratting is a kind of deserting).
'rats' back-to-front is 'STAR'.
Can you help me to learn more?
(Other definitions for star that I've seen before include "See 5" , "White blaze on a horse's forehead" , "Sign of a leading performer" , "Public figure" , "Pointed symbol" .)