Sending first last in the final parts (7)
I believe the answer is:
endings
'the final parts' is the definition.
(I've seen this before)
'sending first last in' is the wordplay.
'sending' becomes 'gs' (I am not sure about this - if you are sure you should believe this answer much more).
'first' means one lot of letters go next to another.
'last' becomes 'end' (I've seen this in another clue).
'end'+'in'='endin'
'gs' put after 'endin' is 'ENDINGS'.
Can you help me to learn more?
(Other definitions for endings that I've seen before include "Closings, terminations" , "Final parts" , "Closures" , "Finishes" , "Suffixes" .)