Step 1: Understand the word.
"Candid" means being open, frank, and truthful, especially when expressing opinions or facts without concealment.
Step 2: Evaluate the options.
"Tight" means restricted or close-fitting; "happy" means cheerful; "strict" means demanding adherence to rules -- none of these relate to truthfulness.
Step 3: Choose the synonym.
"Honest" means truthful and straightforward, making it the closest synonym for candid. \[ \boxed{\text{honest}} \]