Ringleader put in charge is unrestricted (4)
I believe the answer is:
free
'unrestricted' is the definition.
(similar in meaning)
'ringleader put in charge' is the wordplay.
'ringleader' becomes 'r' (first letter of ring).
'put in' is an insertion indicator.
'charge' becomes 'fee' (fee is a kind of charge).
'r' inserted into 'fee' is 'FREE'.
'is' is the link.
(Other definitions for free that I've seen before include "Not restricted or controlled" , "like some public houses" , "Release; gratis" , "Not occupied; release" , "At liberty" .)