One helping Horatio Nelson, to some extent (6)
I believe the answer is:
ration
'one helping' is the definition.
(thesaurus)
'horatio nelson to some extent' is the wordplay.
'to some extent' indicates the answer is hidden within the clue.
'RATION' can be found hidden inside 'horatio nelson'.
(Other definitions for ration that I've seen before include "Fixed restricted allowance" , "Limit quantity as of food during scarcity" , "A fixed quantity allowed to one person in times of scarcity" , "Food apportionment" , "Wartime allowance?" .)