As south you raise yourself to game due to the suposed double fit with diamonds (wrong) and your club short where opponent's probably have many honnors (right).
LHO leads ♣6, RHO wins ♣A and returns ♣5, you ruff and LHO plays ♣2.
Tips for intermediates:
Spoiler
After tackling trumps you will see that RHO has ♥Q10x and LHO singleton (pitches a club)
What next?
More tips for intermediates:
Spoiler
LHO pitches ♦5 while RHO wins. he plays ♦Q back.
With all the deductions made so far, making the best play next shouldn't be hard.