Jumbo shot within the month (7)
I believe the answer is:
mammoth
'jumbo' is the definition.
(thesaurus)
'shot within the month' is the wordplay.
I cannot quite see how this works, but
'shot' could be 'ammo' (ammunition) and 'ammo' is present in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
'month' could be 'm' (standard abbreviation) and 'm' is found in the answer.
A single letter 'h' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for mammoth that I've seen before include "Extinct shaggy-haired elephant" , "Brobdingnagian" , "Prehistoric beast like hairy elephant" , "Extinct species of elephant" , "Prehistoric woolly elephant" .)