Shrill and voracious, but not at first (5)
I believe the answer is:
reedy
'shrill' is the definition.
(I've seen this before)
'voracious but not at first' is the wordplay.
'voracious' becomes 'greedy' (I've seen this before).
'but not at first' means to remove the first letter.
'greedy' with its initial letter taken away is 'REEDY'.
'and' acts as a link.
(Other definitions for reedy that I've seen before include "Long and thin" , "Sounding like eg oboe" , "Of voice, having thin high tone" , "That'll sound a bit thin" , "(Of sound) thin in tone" .)