Go very softly around central Harlesden (3)
I believe the answer is:
pep
'go' is the definition.
(thesaurus)
'very softly around central harlesden' is the wordplay.
'very softly' becomes 'pp' (abbreviation for pianissimo - very quietly).
'around' is an insertion indicator.
'central' means to look at the middle letters.
The centre of 'harlesden' is 'e'.
'pp' enclosing 'e' is 'PEP'.
(Other definitions for pep that I've seen before include "savings plan" , "Palindrome for vitality or energy" , "Palindromic energy or vim" , "Energy, zip" , "Palindrome for vigour" .)