Unkind, short row is more powerful (7)
I believe the answer is:
meatier
'more powerful' is the definition.
Both the answer and definition are comparative adjectives. Maybe you can see an association between them that I can't see?
'unkind short row' is the wordplay.
'unkind' becomes 'mean' (I've seen this before).
'short' means to remove the last letter.
'row' becomes 'tier' (a tier is a row of things).
'mean' with its last letter taken away is 'mea'.
'mea'+'tier'='MEATIER'
'is' is the link.
Can you help me to learn more?
(Other definitions for meatier that I've seen before include "having more muscle" , "Having more flesh" , "More substantial - emirate (anag)" , "More brawny" .)