What is meant by assured seed set?

Dear student, 
​Please find below the solution to the asked query  

Assured seed set means that some seeds are produced are produced by the plant even in unfavourable conditions. It is a type of guarantee or assurance that is provided by cleistogamy.

Cleistogamy may allow the plant to reproduce even in poor conditons and assures some seed set even in conditions unfavourable to plant growth.     

Pea plants undergo self pollination, hence they also produce assured seed sets.

Hope this information will clear your doubts about the topic.    Regards