Politician's period in power little welcomed by nurse (7,8)
I believe the answer is:
foreign minister
'politician's' is the definition.
(I've seen this before)
'period in power little welcomed by nurse' is the wordplay.
'period in power' becomes 'reign' (I've seen this before).
'little' becomes 'mini'.
'welcomed by' indicates putting letters inside (I've seen this in other clues).
'nurse' becomes 'foster' (I've seen this before).
'reign'+'mini'='reignmini'
'reignmini' inserted into 'foster' is 'FOREIGN MINISTER'.
(Other definitions for foreign minister that I've seen before include "Angela Merkel, for instance" , "Straw was" , "Senior politician" , "Powerful person in government" , "churchman from Rome?" .)