Small child, we hear, displaying strength (5)
I believe the answer is:
might
'strength' is the definition.
(I know that might is a type of strength)
'small child we hear' is the wordplay.
'small child' becomes 'mite' (informal term).
'we hear' shows a homophone (sound like).
'mite' sounds like 'MIGHT'.
'displaying' is the link.
(Other definitions for might that I've seen before include "intensity of feeling" , "word expressing possibility" , "Great power, strength" , "Strength - could possibly" , "Great power/strength" .)