Assuming the 5 card hand is dealt from a standard randomly shuffled deck of 52 cards, the probability of getting a hand with 5 clubs is
[tex]\dfrac{\dbinom{13}5\dbinom{39}0}{\dbinom{52}5}=\dfrac{\dbinom{13}5}{\dbinom{52}5}=\dfrac{33}{66640}\approx0.000495[/tex]