Tool has blade: hard to smuggle into jail (12)
I believe the answer is:
sledgehammer
'tool' is the definition.
(sledgehammer is a kind of tool)
'blade hard to smuggle into jail' is the wordplay.
'blade' becomes 'edge' (as in a sharpened edge).
'hard' becomes 'h' (abbreviation used in pencil classifications).
'to smuggle into' means one lot of letters goes inside another.
'jail' becomes 'slammer' (informal term for prison).
'edge'+'h'='edgeh'
'edgeh' inserted within 'slammer' is 'SLEDGEHAMMER'.
'has' is the link.
(Other definitions for sledgehammer that I've seen before include "Unsubtle" , "One violently smashing" , "Tool" , "Big hitter" , "Unsuitable nutcracker?" .)