Urge on the leading intellectual? (7)
I believe the answer is:
egghead
'intellectual?' is the definition.
(I know that egghead is a type of intellectual)
'urge on the leading' is the wordplay.
'urge' becomes 'egg' (as in egging someone on).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'the leading' becomes 'head' (I've seen this in other clues).
'egg'+'head'='EGGHEAD'
(Other definitions for egghead that I've seen before include "Intellectual - highbrow" , "Very academic person" , "Very clever person" , "An intellectual (inf.)" , "providing access to soldiers" .)