Adjectives are words which describe something,words like important,red,blue,angry are adjectives.
That book is blue is color,
In the above sentence,the word "blue" is describing how the book looks like.Blue is an adjective here.
In adjective clause,you just have to complete the given sentence using adjectives.
Ravi works for a company....................
you just have to complete the sentence,you can do it like
Ravi works for a company which is very big.
Ravi works for a company which is one of the leading companies of India
Ravi works for a company where all the employees are treated equally.
Ravi works for a company that is very reputed.