Faltered at, so I put it in Greek letters (5)
I believe the answer is:
iotas
'greek letters' is the definition.
(I've seen this in another clue)
'faltered at so i put it' is the wordplay.
'faltered' is an anagram indicator (I've seen 'faltering' mean this).
'at' says to put letters next to each other.
'i' becomes 'a'.
'put' says to put letters next to each other.
'so'+'a'='soa'
'soa' after 'it' is 'itsoa'.
'itsoa' is an anagram of 'IOTAS'.
'in' is the link.
(Other definitions for iotas that I've seen before include "Jots, very small amounts" , "Tiny amounts" , "Tiny scraps" .)