Dog in need of lead — that's worth having (5)
I believe the answer is:
asset
'that's worth having' is the definition.
(an asset is something valuable or useful)
'dog in need of lead' is the wordplay.
'dog' becomes 'basset' (type of dog).
'in need of lead' means to remove the first letter (the letter that leads the word is removed).
'basset' with its initial letter taken off is 'ASSET'.
(Other definitions for asset that I've seen before include "Useful thing or person" , "Seats (anag.)" , "Someone or something of value" , "Useful or valuable property" , "Plus point" .)