Relax around mound (5)
I believe the answer is:
chill
'relax' is the definition.
(I've seen this in another clue)
'around mound' is the wordplay.
'around' becomes 'c' (abbreviation for 'circa').
'mound' becomes 'hill' (synonyms).
'c'+'hill'='CHILL'
(Other definitions for chill that I've seen before include "Sensation of cold or dread" , "Iciness" , "Feverish cold; relax" , "This disheartens" , "Refrigerate" .)