Is it possible to assign a value where the target is itself a variable

Question

If I have a variable x := "a".
Is there a way I can use it to assign a value to a, by just referring to x?
If I try Evaluate[x]=4 I get error messages about Tag Times in x Null is protected.
I would like some way of having it execute a = 4.

Answer 1

adding one more and summarizing comments

     ToExpression[x <> "=" <> ToString[10]];

or

     ToExpression[StringJoin @@ ToString /@ {x, "=", 3.14}]

from: @LeonidShifrin

     ToExpression[x, StandardForm, Function[var, var = 42, HoldFirst]]

@belisarius approach only works once:

     Evaluate@Symbol[x] = 1

after "a" has a value, Symbol[x] returns the value so this breaks if you try to use it more than once.

@kuba proposes using TagSetDelayed x:

     x := "a" 
     x /: Set[x, y_] := Set[a, y]

which will let you simply do:

     x=3

with the result being assignment of "a" {x,a} -> {"a",3}