Move slowly in Winchester (4)
I believe the answer is:
inch
'move slowly' is the definition.
(to inch along is to move slowly)
'in winchester' is the wordplay.
'in' indicates a hidden word.
'INCH' is hidden in the letters of 'winchester'.
(Other definitions for inch that I've seen before include "2.45 cm" , "The island is very small in length" , "Small Scottish island" , "Thirty-sixth of yard" , "2.54 cm (approx.)" .)