Medallion omitting first name would lead one to complain (7)
I believe the answer is:
pendant
'medallion' is the definition.
(thesaurus)
'omitting first name would lead one to complain' is the wordplay.
I cannot really see how this works, but
'first' could be 'a' (first letter of the alphabet) and 'a' is found in the answer.
'name' could be 'pen' and 'pen' is found within the answer.
'would' could be 'd' (I've seen this in other clues) and 'd' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for pendant that I've seen before include "Hanging jewellery item" , "earring, say" , "One hung by the neck" , "Ornament hanging from necklace" , "item suspended" .)