Ring Eric about touring Cornwall on vacation (6)
I believe the answer is:
circle
'ring' is the definition.
(synonyms)
'eric about touring cornwall on vacation' is the wordplay.
'about' says the letters should be written backwards.
'touring' means one lot of letters goes inside another (touring can mean going round).
'on vacation' suggests removing the centre.
'cornwall' with its middle removed is 'cl'.
'eric' back-to-front is 'cire'.
'cire' enclosing 'cl' is 'CIRCLE'.
(Other definitions for circle that I've seen before include "Curved figure" , "Geometric shape" , "Go round -- social group" , "Perfect round" , "Theatre seating tier" .)