I think it's about someone who wants to have a relationship with someone underage ("My, you have grown", "You will only come of age") but their affections are unrequited ("Give me some recognition"). But that love is bordering on obsession ("Who are you fooling, your heart is bleeding"). "No cars facing our way" is probably them trying to reassure that they won't get in trouble for the relationship, that no one will find out and they'll keep it going behind people's backs. And melting away probably means sex.
I think it's about someone who wants to have a relationship with someone underage ("My, you have grown", "You will only come of age") but their affections are unrequited ("Give me some recognition"). But that love is bordering on obsession ("Who are you fooling, your heart is bleeding"). "No cars facing our way" is probably them trying to reassure that they won't get in trouble for the relationship, that no one will find out and they'll keep it going behind people's backs. And melting away probably means sex.