It's my shakiness that gives you a vague clue (5)
I believe the answer is:
'gives you a vague clue' is the definition.
I can't tell whether this definition defines the answer.
'it's my shakiness' is the wordplay.
'it's my' anagrams to 'MISTY'.
Though, I'm not sure how the anagram is indicated.
'that' is the link.
Can you help me to learn more?
(Other definitions for misty that I've seen before include "Cloudy, foggy" , "Dim, indistinct" , "unclear" , "Slightly fogged" , "Indistinct in outline" .)