Even mummy quietly puts on top back to front and succeeds! (8)

'succeeds' is the definition.

'even mummy quietly puts on top back to front' is the wordplay.
'even' means one should take alternating letters (even-numbered letters are used).
'quietly' becomes 'p' (p for piano and quiet).
'puts on' means one lot of letters goes inside another (some letters put on or wear other letters).
'top' becomes 'shirt' (**).
'back to front' shows that the letters should be reversed in order.
The alternate letters of 'mummy' are 'um'.
'shirt' back-to-front is 'trihs'.
'um'+'p'='ump'
'ump' inserted within 'trihs' is 'TRIUMPHS'.

'and' acts as a link.