Like one of three needing holiday permit? (7)
I believe the answer is:
triplet
'like one of three' is the definition.
'triplet' can be an answer for 'three' (synonyms). I'm not sure about the 'like one of' bit.
'holiday permit?' is the wordplay.
'holiday' becomes 'trip' (I've seen this before).
'permit?' becomes 'let' ('let' can be a synonym of 'permit').
'trip'+'let'='TRIPLET'
'needing' acts as a link.
Can you help me to learn more?
(Other definitions for triplet that I've seen before include "One of three born at the same time" , "One of a set of three" , "Set of three things" , "One of a group of three" , "Member of large family" .)