Wild boars on an island shown on certain charts (7)
I believe the answer is:
isobars
'on certain charts' is the definition.
Although both the answer and definition are plural nouns, I can't understand how one could define the other.
'wild boars on an island' is the wordplay.
'wild' indicates an anagram.
'on' indicates putting letters inside.
'an island' becomes 'is' (abbreviation).
'boars' with letters rearranged gives 'sobar'.
'sobar' put into 'is' is 'ISOBARS'.
'shown' is the link.
Can you help me to learn more?
(Other definitions for isobars that I've seen before include "Lines on map indicating atmospheric pressure" , "15 is strong when they are close" , "Map lines of equal pressure" , "can show what pressure folk are under" , "Lines of equal atmospheric pressure" .)