Wilful leaders of dangerous enterprise get set free (10)
I believe the answer is:
deliberate
'wilful' is the definition.
(synonyms)
'leaders of dangerous enterprise get set free' is the wordplay.
'leaders of' indicates taking the first letters.
'get' says to put letters next to each other.
'set free' becomes 'liberate' (synonyms).
The first letters of 'dangerous enterprise' is 'de'.
'de'+'liberate'='DELIBERATE'
(Other definitions for deliberate that I've seen before include "Intentional; think carefully" , "Consider carefully" , "Well considered" , "Planned" , "muse" .)