P, Q, R, S, T and U each have different weights. S is heavier than Q. R is lighter than only T and P. Q is not the lightest and P is not the heaviest. Who is the second heaviest in terms of weight?

P

S is heavier than Q =>  S > Q

R is lighter than only T and P. This means R is the 3rd heaviest.

Q is not the lightest. This means there is atleast one person heavier than P.

So, from 2nd statement, T and P are two heaviest and from 3rd statement, P is not the heaviest. 

So, T must be the heaviest.

Thus, P is the second heaviest.

=> T > P > R

Thus, P is the 2nd heaviest in terms of weight.