안녕하세요^^ Tania 님!
You are so right on 한 발짝 물러서다 it is a step back :-)
"자꾸 한 발짝만 물러서 달래"
We can take a closer look!
자꾸 again and again / keep Ving
한 발짝 a step
물러서다 to back off /to step back
-아/어 달래 it indicates that you are telling someone that person A tells/asks person B/you to V.
So literally, He/She keeps telling me to step back
but it can be used in different situations.
if it is lyrics, it would probably mean not to rush in loving the other like slowing down ;-)
Hope this helps you a bit!