A country once in centre of stormy peninsula (4,5)
I believe the answer is:
asia minor
'peninsula' is the definition.
(Asia Minor is an example)
'a country once in centre of stormy' is the wordplay.
'country once' becomes 'siam' (former name of Thailand).
'centre of' means to look at the middle letters.
The middle letters of 'stormy' are 'or'.
'a'+'siam'+'in'+'or'='ASIA MINOR'
(Other definitions for asia minor that I've seen before include "Historical land" , "part of Turkey" , "Historical name for Anatolia" , "Alternative name for Anatolia" , "several?" .)