Thin and weak, wanting lots of food but no starter (5)
I believe the answer is:
reedy
'thin and weak' is the definition.
(I've seen this before)
'wanting lots of food but no starter' is the wordplay.
'wanting lots of food' becomes 'greedy'.
'but no starter' means to remove the first letter.
'greedy' with its first letter taken away is 'REEDY'.
(Other definitions for reedy that I've seen before include "Piping, fluting" , "Like some of the wind" , "abounding with grasses" , "Sounding like eg oboe" , "Like some pipes" .)