Recognise by silhouette and realise what's right to do (4,3,4)

'recognise by silhouette' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'realise what's right to do' is the wordplay.
I cannot really understand how this works, but
'realise' could be 'know' (I've seen this before) and 'know' is found in the answer.
'right' could be 'r' (common abbreviation) and 'r' is found within the answer.
This explanation may well be incorrect...

'and' acts as a link.

Can you help me to learn more?