If you play alongwith a person, with what they say, or with their plans, you appear to agree with them and do what they want, even though you are not sure whether they are right.
My mother has learnt to play along with the bizarre conversations begun by father. [VERBPARTICLE + with]
He led the way to the lift. Fox played along, following him. [VERBPARTICLE]
See full dictionary entry for play
play along in British English
verb(adverb)
1. (intransitive; usually foll bywith)
to cooperate (with), esp as a temporary measure
2. (transitive)
to manipulate as if in a game, esp for one's own advantage
he played his victims along until they gave him their money
Examples of 'play along' in a sentence
play along
They all played along although one or two needed help with a name they had forgotten.
Times, Sunday Times (2016)
You play along with social games which you feel deeply disconnected from and I can feel your pain.
The Sun (2010)
Used to love to listen to the Chicago symphony, and he wanted to play along.
Christianity Today (2000)
I don't want to be played along but my son loves him and won't want him to go.