Fooled Frenchman with one sleigh (6)
I believe the answer is:
misled
'fooled' is the definition.
(I've seen this in another clue)
'frenchman with one sleigh' is the wordplay.
'frenchman' becomes 'm' (abbreviation for Monsieur - like 'Mr').
'with' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'sleigh' becomes 'sled' (synonyms).
'm'+'i'+'sled'='MISLED'
(Other definitions for misled that I've seen before include "Sent in the wrong direction or deceived" , "Gave false or misleading information to" , "Sent astray or gave wrong impression" , "Given the wrong impression" , "taken for a ride" .)