A segment of the gene manipulated in an uncomfortable medical procedure (5)
I believe the answer is:
enema
'medical procedure' is the definition.
(I've seen this before)
'a segment of the gene manipulated in' is the wordplay.
'a segment of' says the answer is hidden in the clue (I've seen this in other clues).
'ENEMA' can be found hidden inside 'gene manipulated in'.
'an uncomfortable' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for enema that I've seen before include "Stern action from nurse perhaps" , "The bottom line in medical treatment?" , "fundamental procedure?" , "Fluid injected rectally" , "Liquid injection given as a laxative" .)