Herb forming part of healthy meal (5)
I believe the answer is:
thyme
'herb' is the definition.
(thyme is a kind of herb)
'part of healthy meal' is the wordplay.
'part of' indicates a hidden word.
'THYME' is hidden in the letters of 'healthy meal'.
'forming' is the link.
(Other definitions for thyme that I've seen before include "Flavouring" , "Small shrub with minty odour" , "Kind of mint" , "Strong herb" , "Leaves used as seasoning" .)