Link to a big country (4)
I believe the answer is:
laos
'country' is the definition.
(I know that Laos is a country)
'link to a big' is the wordplay.
'link' becomes 'l' (this might be a standard abbreviation I've not previously seen).
'big' becomes 'os' (abbreviation for oversize).
'l'+'a'+'os'='LAOS'
Can you help me to learn more?
(Other definitions for laos that I've seen before include "Republic in southeastern Asia" , "Country between Thailand/Vietnam" , "South-east Asian republic, capital Vientiane" , "Country of SE Asia" , "part of Asia" .)