Held the letter that was torn (7)

I believe the answer is:
gripped
'held the letter that' is the definition.
'gripped' can be an answer for 'held' (thesaurus). I am not sure about the rest of the definition.
'was torn' is the wordplay.
'was' becomes 'g' (I can't explain this - if you can you should believe this answer much more).
'torn' becomes 'ripped' (ripping is a kind of tearing).
'g'+'ripped'='GRIPPED'
Can you help me to learn more?
(Other definitions for gripped that I've seen before include "Held fast or firmly" , "Seized or held firmly" , "was fascinating" .)
