Look at and read aloud the letter (3)
I believe the answer is:
eye
'look at' is the definition.
'read aloud the letter' is the wordplay.
'read aloud' shows a homophone (sound like).
'the letter' becomes 'i'.
'i' is a homophone of 'EYE'.
'and' is the link.
(Other definitions for eye that I've seen before include "Viewer" , "'Cast a cold ... on life, on death' (Yeats)" , "round hole in sewer?" , "Small loop or hole" , "Optical organ" .)