Dock is important to auditor (4)
I believe the answer is:
quay
'dock' is the definition.
(quay is a kind of dock)
'important to auditor' is the wordplay.
'important' becomes 'key' (similar in meaning).
'to auditor' indicates a 'sounds like' (homophone) clue (I've seen 'to auditors' mean this (an auditor is a listener)).
'key' is a homophone of 'QUAY'.
'is' is the link.
(Other definitions for quay that I've seen before include "crucial, by the sound of it" , "Landing stage, wharf" , "Landing-place" , "Platform for loading and unloading ships" , "Some of port" .)