Coach first of all drives all over the place (7)
I believe the answer is:
adviser
'coach' is the definition.
'first of all drives all over the place' is the wordplay.
'first of' indicates taking the first letters.
'all over the place' indicates an anagram.
The first letter of 'all' is 'a'.
'drives' anagrammed gives 'dviser'.
'a'+'dviser'='ADVISER'
(Other definitions for adviser that I've seen before include "ID saver (anag.)" , "Counseller" , "subject's specialist consultant" , "Guide" , "Counsellor, mentor" .)