Source of intelligence, say, Government picked up, discounting Russia’s leader (7)
I believe the answer is:
egghead
'source of intelligence' is the definition.
(intelligent person)
'say government picked up discounting russia's leader' is the wordplay.
I cannot quite see how this works, but
'say' could be 'eg' (short for 'exempli gratia', 'for example' in Latin) and 'eg' is located in the answer.
'government' could be 'g' (abbreviation for government) and 'g' is present in the answer.
'leader' could be 'head' (head is a kind of leader) and 'head' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
(Other definitions for egghead that I've seen before include "where soldiers may take a dip?" , "Very academic person" , "Intellectual (colloq.)" , "Intellectual (sl.)" , "Informal intellectual of ovoid type" .)