Shout at infant, a wuss (7)
I believe the answer is:
crybaby
'a wuss' is the definition.
(I know that crybaby is a type of wuss)
'shout at infant' is the wordplay.
'shout' becomes 'cry' (synonyms).
'at' says to put letters next to each other.
'infant' becomes 'baby' (synonyms).
'cry'+'baby'='CRYBABY'
(Other definitions for crybaby that I've seen before include "Person readily shedding tears" , "Person too easily reduced to tears" , "(Very young?) weeper" , "One prone to tears" , "One shedding tears frequently" .)