Good argument finally dealt with hotel development (6)
I believe the answer is:
growth
'development' is the definition.
(growth is a kind of development)
'good argument finally dealt with hotel' is the wordplay.
'good' becomes 'g' (abbreviation).
'argument' becomes 'row' (to row is to argue).
'finally' says to take the final letters.
'with' says to put letters next to each other.
'hotel' becomes 'h' (phonetic alphabet).
The final letter of 'dealt' is 't'.
'g'+'row'+'t'+'h'='GROWTH'
(Other definitions for growth that I've seen before include "Increase - development - tumour" , "Augmentation" , "Development - enlargement" , "Tumour - enlargement" , "Gradual increase" .)