Herb having some lengthy meal (5)
I believe the answer is:
thyme
'herb' is the definition.
(I know that thyme is a type of herb)
'some lengthy meal' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'THYME' can be found hidden inside 'lengthy meal'.
'having' is the link.
(Other definitions for thyme that I've seen before include "Sweet-smelling herb of the mint family" , "Part of song: ''parsley, sage, rosemary and . . . . .''" , "Ingredient in cooking" , "Kind of mint" , "Sage's bedmate" .)