Tiny amplifier Nigeria had developed (7,3)
I believe the answer is:
hearing aid
'tiny amplifier' is the definition.
'hearing aid' can be an answer for 'amplifier' (thesaurus). I am not sure about the 'tiny' bit.
'nigeria had developed' is the wordplay.
'developed' indicates anagramming the letters.
'nigeria'+'had'='nigeriahad'
'nigeriahad' is an anagram of 'HEARING-AID'.
Can you help me to learn more?
(Other definitions for hearing aid that I've seen before include "Amplifier for ear" , "Help for the partially deaf" , "Ear trumpet" , "Earpiece" , "asset in court?" .)