Poet initially stuck in loo turned up (1,1,5)
I believe the answer is:
t s eliot
'poet' is the definition.
(I've seen this before)
'initially stuck in loo turned up' is the wordplay.
'initially' suggests taking the first letters.
'in' is an insertion indicator.
'loo' becomes 'toilet' (I've seen this in another clue).
'turned up' shows that the letters should be reversed in order.
The first letter of 'stuck' is 's'.
's' put inside 'toilet' is 'toilest'.
'toilest' back-to-front is 'T S ELIOT'.
(Another definition for t s eliot that I've seen is " The Waste Land poet".)