Errand boy not following viable plan (4)
I believe the answer is:
goer
'viable plan' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'errand boy not following' is the wordplay.
'errand boy' becomes 'gofer' (I've seen this before).
'not' is a deletion indicator.
'following' becomes 'f.' (used when citing page numbers etc).
'gofer' with 'f' taken out is 'GOER'.
Can you help me to learn more?
(Other definitions for goer that I've seen before include "Lively person -- feasible idea" , "Someone lively" , "Energetic type" , "one trying to succeed" , "Lively energetic person" .)