Large peninsula in part of West Africa (7)
I believe the answer is:
liberia
'part of west africa' is the definition.
(I know that Liberia is part of West Africa)
'large peninsula' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'peninsula' becomes 'Iberia' (peninsula including Spain and Portugal).
'l'+'iberia'='LIBERIA'
'in' is the link.
(Other definitions for liberia that I've seen before include "West African country founded for freed slaves" , "W African Republic" , "Monrovia's country" , "African country, established by the US in 1822" , "West African nation" .)