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 can't judge whether it can be defined by this definition.

'realise what's right to do' is the wordplay.
I cannot quite understand how this works, but
'realise' could be 'know' (I've seen this before) and 'know' is present in the answer.
'right' could be 'r' (common abbreviation) and 'r' is present in the answer.
This may be the basis of clue (or it may be nonsense).

'and' acts as a link.

Can you help me to learn more?