Reduce by ha'pence somehow (7)
I believe the answer is:
cheapen
'reduce' is the definition.
(thesaurus)
'ha'pence somehow' is the wordplay.
'somehow' indicates an anagram.
'hapence' anagrammed gives 'CHEAPEN'.
'by' acts as a link.
(Other definitions for cheapen that I've seen before include "lower" , "Depreciate" , "Decry or devalue" , "decrease in value" , "Reduce worth, degrade" .)