Welshman losing footing on platform (3)
I believe the answer is:
dai
'welshman' is the definition.
(Welsh name)
'losing footing on platform' is the wordplay.
'losing footing on' means to remove the last letter (the letter at the foot of the word is removed).
'platform' becomes 'dais' (dais is a kind of platform).
'dais' with its final letter removed is 'DAI'.
(Other definitions for dai that I've seen before include "Lloyd George?" , "Welshman's name" , "Welshman" , "Perhaps man in Cardiff" , "Welsh male name" .)