Call struct overrload output inside class overrload output

This is my code:

 struct Term{

   int coeff;
   int expo;
   Term* next;
   friend ostream& operator<<(ostream& os, const Term& rt);
 };

class Polynomial{

  public:
    Term *head;
    Polynomial();
    friend ostream& operator<<(ostream& os, const Polynomial& a_poly);
};

How can I use  use the operator<< function defined for the Term  struct inside operator << function defined for Polynomial Class ?