Guide showing king round centre of Aden (6)
I believe the answer is:
leader
'guide' is the definition.
(thesaurus)
'king round centre of aden' is the wordplay.
'king' becomes 'lear' (I've seen this before).
'round' indicates putting letters inside.
'centre of' says to take the centre.
The centre of 'aden' is 'de'.
'lear' going around 'de' is 'LEADER'.
'showing' acts as a link.
(Other definitions for leader that I've seen before include "Party head" , "Opinion piece; boss" , "Pioneer" , "Principal first violinist" , "Head (of government, etc)" .)