The nod from principal for a local job (4,5)
I believe the answer is:
head start
'the nod' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'principal for a local job' is the wordplay.
'principal' becomes 'head' ('head' can be a synonym of 'principal').
'for' means one lot of letters go next to another.
'a local job' becomes 'start' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'head'+'start'='HEAD START'
'from' is the link.
Can you help me to learn more?
(Other definitions for head start that I've seen before include "Boost?" , "A good beginning using one's loaf" , "'The advantage of beginning ahead of others (4,5)'" , "Substantial initial advantage" , "An early advantage for the star ad" .)