Small relative gets least (7)
I believe the answer is:
minimum
'least' is the definition.
(similar in meaning)
'small relative' is the wordplay.
'small' becomes 'mini' (short for miniature).
'relative' becomes 'mum' (mum is a kind of relative).
'mini'+'mum'='MINIMUM'
'gets' is the link.
(Other definitions for minimum that I've seen before include "Nadir" , "Smallest possible quantity" , "Bottom" , "Lowest value" , "Least possible quantity" .)