Dexterity shown by the French in view of worker (7,2,4)
I believe the answer is:
sleight of hand
'dexterity' is the definition.
(I've seen this before)
'the french in view of worker' is the wordplay.
'the french' becomes 'le' ('the' in French).
'in' means one lot of letters goes inside another.
'view' becomes 'sight' (synonyms).
'worker' becomes 'hand' (hand is a kind of worker).
'le' inserted within 'sight' is 'sleight'.
'sleight'+'of'+'hand'='SLEIGHT-OF-HAND'
'shown by' acts as a link.
(Other definitions for sleight of hand that I've seen before include "Legerdemain" , "Prestidigitation" , "Conjuror's skill" , "Doctor or student doctor" , "Manual dexterity in conjuring" .)