Game on jetty? What could be more eccentric? (7)
I believe the answer is:
loopier
'more eccentric?' is the definition.
'game on jetty?' is the wordplay.
'game' becomes 'loo' (historic card game found in Jane Austen novels**).
'on' means one lot of letters go next to another.
'jetty?' becomes 'pier' (I've seen this before).
'loo'+'pier'='LOOPIER'
'what could be' is the link.
(Other definitions for loopier that I've seen before include "Dafter" , "more unbalanced" , "More crazy" , "less stable" .)