A blog claimed Ben Foday said he was "very against" gay marriage, at a Cardiff South and Penarth constituency hustings.
He has since told BBC Wales he was asked to comment on laws being passed without proper consultation, or without the policy being in a party manifesto.
Mr Foday said he "fully supports" gay marriage and "equal rights".
"In the hustings I was asked for my view on parliament passing legislation without proper consultation, or without the policy having been in the party's manifesto, I said that I was against that," Mr Foday said.
"I am sorry if this was interpreted to mean that I was against gay marriage.
"That is certainly not the case, I fully support gay marriage and equal rights," he added.
A full list of candidates standing in Cardiff South and Penarth can be seen here.
A Plaid Cymru election candidate has said he is sorry if a remark he made about gay marriage was misinterpreted.