Lukewarm food served up, including pitiful starter (5)
I believe the answer is:
tepid
'lukewarm' is the definition.
(I know that lukewarm can be written as tepid)
'food served up including pitiful starter' is the wordplay.
'food' becomes 'diet' (diet is a kind of food).
'served up' says the letters should be written in reverse (in a down clue, going upwards).
'including' is an insertion indicator.
'starter' suggests taking the first letters.
The first letter of 'pitiful' is 'p'.
'diet' backwards is 'teid'.
'teid' going around 'p' is 'TEPID'.
(Other definitions for tepid that I've seen before include "Not very warm (water)" , "What's a bit warm" , "Of liquid, luke-warm" , "without passion" , "without enthusiasm" .)