Clue: Emblem of South Africa: river within a river with drink (6)
Answer: PROTEA
Explanation: Definition: Emblem of South Africa
An envelope ('within') of R (the first 'river') in PO ('a river') plus TEA ('drink'). The has a stylised Protea above the crossed spear and knobkierrie, and merging into the secretary bird. Protea cynaroides, King Protea. Photo Bernard Spragg