Tinier moves by a sloth (7)
I believe the answer is:
inertia
'sloth' is the definition.
(inertia can mean laziness or sloth)
'tinier moves by a' is the wordplay.
'moves' is an anagram indicator.
'by' means one lot of letters go next to another.
'tinier' is an anagram of 'inerti'.
'inerti'+'a'='INERTIA'
(Other definitions for inertia that I've seen before include "Way of selling" , "Slowness to take action, state of laziness" , "I earn it (anag.)" , "Resistance to motion" , "Resistance to change" .)