Unnecessary self-starter follows tools for sewers (8)
I believe the answer is:
needless
'unnecessary' is the definition.
(similar in meaning)
'tools for sewers' is the wordplay.
'tools' becomes 's' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'for' means one lot of letters go next to another (I've seen this in other clues).
'sewers' becomes 'needles' (I've seen this before).
's' put after 'needles' is 'NEEDLESS'.
'self-starter follows' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for needless that I've seen before include "Surplus to requirements" , "Lessened, being without good cause" , "Unnecessary, avoidable" , "Unneccessary and unwarranted" , "luxury" .)