False teeth regularly scrubbed fast (5)
I believe the answer is:
fleet
'fast' is the definition.
(similar in meaning)
'false teeth regularly scrubbed' is the wordplay.
'regularly scrubbed' means one should take alternating letters (letters removed at regular intervals).
'false'+'teeth'='falseteeth'
The alternate letters of 'falseteeth' are 'FLEET'.
(Other definitions for fleet that I've seen before include "Fast; London street, old prison" , "Swift like naval force" , "Fast kind of armada?" , "fast is observed" , "Group of ships, aircraft etc" .)