Puppy initially wants assistance (5)
I believe the answer is:
whelp
'puppy' is the definition.
(thesaurus)
'initially wants assistance' is the wordplay.
'initially' indicates taking the first letters.
'assistance' becomes 'help' ('help' can be a synonym of 'assistance').
The initial letter of 'wants' is 'w'.
'w'+'help'='WHELP'
(Other definitions for whelp that I've seen before include "Have puppies" , "Perform deliveries without assistance" , "bear" , "youngster" , "impudent young lad" .)