Thinking of strange island state (10)
I believe the answer is:
rumination
'thinking' is the definition.
(rumination is a kind of thinking)
'strange island state' is the wordplay.
'strange' becomes 'rum' (I've seen this before).
'island' becomes 'i'.
'state' becomes 'nation' ('nation' can be a synonym of 'state'**).
'rum'+'i'+'nation'='RUMINATION'
'of' is the link.
(Other definitions for rumination that I've seen before include "Thought" , "thinking" , "Musing" .)