Little pest has power we hear (4)
I believe the answer is:
mite
'little' is the definition.
(thesaurus)
'power we hear' is the wordplay.
'power' becomes 'might' (synonyms).
'we hear' indicates a 'sounds like' (homophone) clue.
'might' sounds like 'MITE'.
'pest has' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for mite that I've seen before include "Tiny creature found in food" , "The widow's small offering" , "Microscopic animal" , "Very small creature or child" , "Tiny arachnid, person or amount of money" .)