Docker set off, drove erratically close to edge (9)
I believe the answer is:
stevedore
'docker' is the definition.
('stevedore' can be a synonym of 'docker')
'set off drove erratically close to edge' is the wordplay.
'off' is an anagram indicator.
'erratically' indicates an anagram.
'close to' suggests the final letters (the close/ending of).
The last letter of 'edge' is 'e'.
'set' anagrammed gives 'ste'.
'drove' is an anagram of 'vedor'.
'ste'+'vedor'+'e'='STEVEDORE'
(Other definitions for stevedore that I've seen before include "One is employed at a dock to load and unload ships" , "One loads and unloads ships" , "Docker" , "one working in docks" , "dock pay for him?" .)