A word used by the Pakistani/kashmiri community which means best friend or bad boy or stand up guy or old skool or trustworthy. All of the connotations of the word depend on the circumstances and situations it is applied in. The word was born in the early eighties in Luton in Bedfordshire. Made famous by the then Bury Park Posse who bastardised a word from the Pahari language 'Gandu' which means someone who gets sodomised out of choice or force. 'Andu' then became the opposite of 'Gandu' to show the one who gets it done to him or her is less in stature than the one who does the act of sodomy. It then evolved and the meaning has now become common as described above.
You know that brotha over there he's a proper andu.