1.doing作后置定语,相当于定语从句,doing的执行者是前面的先行词a partner;
如果是practising,就是partner是practise的执行者.
2.作定语的不定式很多与被修饰词在逻辑上是动宾关系.
I want to get something to read during the vacation.
She usually has a lot of meeting to attend in the evenings.
注：如果不定式是不及物动词,后面加介词.
There is nothing to worry about.