Nile net breaks: it's merciful (7)
I believe the answer is:
lenient
'merciful' is the definition.
(synonyms)
'nile net breaks' is the wordplay.
'breaks' indicates anagramming the letters.
'nile'+'net'='nilenet'
'nilenet' anagrammed gives 'LENIENT'.
'it's' acts as a link.
(Other definitions for lenient that I've seen before include "Forgiving, soft" , "Forgiving, gentle" , "Merciful or easygoing" , "Tolerant, rather than strict" , "Mild and tolerant" .)