In contact with foreign leader this month (7)
I believe the answer is:
against
'in contact with' is the definition.
(thesaurus)
'foreign leader this month' is the wordplay.
'foreign leader' becomes 'aga' (historical term for a Muslim military commander).
'this month' becomes 'inst' (I've seen this before).
'aga'+'inst'='AGAINST'
(Other definitions for against that I've seen before include "In competition with" , "In disagreement with" , "Not in favour of" , "Disapproving of" , "V" .)