Could he possibly keep a gang leader in line? (5)
I believe the answer is:
nigel
'line?' is the definition.
Both the answer and definition are singular nouns.
Maybe they are linked in a way I don't understand?
'could he possibly keep a gang leader' is the wordplay.
'could he possibly' becomes 'niel' (I can't justify this - if you can you should believe this answer much more).
'keep' means one lot of letters goes inside another.
'leader' indicates taking the first letters.
The initial letter of 'gang' is 'g'.
'niel' placed around 'g' is 'NIGEL'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for nigel that I've seen before include "Fellows sometimes called this" , "We all sign on (anag) -- politician" , "boy" , "-- Kennedy, violinist" , "Chap" .)