This convert expressing thanks would be silent (6)
I believe the answer is:
mutate
'this convert' is the definition.
(I've seen this before)
'thanks would be silent' is the wordplay.
I cannot really understand how this works, but
'thanks' could be 'ta' (UK informal version of 'thank you') and 'ta' is located in the answer.
'silent' could be 'mute' (synonyms) and 'mute' is located in the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
'expressing' is the link.
Can you help me to learn more?
(Other definitions for mutate that I've seen before include "Undergo genetic change" , "(In genetics) change" , "Undergo change to another form" , "Change genetically" , "Me taut? (anag) - change fundamentally" .)