Put on weight
'put on weight' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for gain that I've seen before include "Profit; acquire" , "Benefit; put on (weight)" , "Advance" , "Obtain; earn" , "Obtain, secure" .)
'put on weight' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for fatten that I've seen before include "Make plump" , "Make chubbier" .)