They give injections but are almost unnecessary (7)
I believe the answer is:
needles
'they give injections but' is the definition.
The definition suggests an adverb but the answer is not.
'almost unnecessary' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'unnecessary' becomes 'needless' (similar in meaning).
'needless' with its final letter taken away is 'NEEDLES'.
'are' is the link.
Can you help me to learn more?
(Other definitions for needles that I've seen before include "Annoys the pointed implements?" , "Sewers; annoys" , "Where a lighthouse is" , "They may play LPs" , "landmark" .)