Hold sway in Niger with difficulty (5)
I believe the answer is:
reign
'hold sway' is the definition.
(I've seen this before)
'niger with difficulty' is the wordplay.
'with difficulty' indicates anagramming the letters.
'niger' is an anagram of 'REIGN'.
'in' acts as a link.
(Other definitions for reign that I've seen before include "Sovereign's rule" , "Period during which someone is dominant" , "Time on throne" , "Dominion" , "Control" .)