Nominal builder of the line around Gateshead (5)
I believe the answer is:
nigel
'nominal builder' is the definition.
The definition suggests a singular noun which matches the answer.
'of the line around gateshead' is the wordplay.
'of' is an anagram indicator (the answer comes from or 'of' the letters).
'around' is an insertion indicator.
'gateshead' becomes 'g' (head letter of 'gates').
'line' is an anagram of 'niel'.
'niel' going around 'g' is 'NIGEL'.
Can you help me to learn more?
(Other definitions for nigel that I've seen before include "-- Gresley, railway engineer" , "Fellows sometimes called this" , "Sir - - Hawthorne, actor" , "man?" , "-- Kennedy, violinist" .)