I am taking mother up to Muslim leader (4)
I believe the answer is:
imam
'muslim leader' is the definition.
(I've seen this before)
'i am taking mother up' is the wordplay.
'i am' becomes 'im' (**).
'taking' says to put letters next to each other.
'mother' becomes 'ma' (ma is a kind of mother).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'ma' backwards is 'am'.
'im'+'am'='IMAM'
'to' acts as a link.
(Other definitions for imam that I've seen before include "Strict religious leader" , "Islamic minister" , "Muslim religious leader" , "Accompaniment in baroque music" , "Moslem prayer leader" .)