Must I use loan up at the same time? (12)
I believe the answer is:
simultaneous
'at the same time?' is the definition.
(synonyms)
'must i use loan up' is the wordplay.
'up' indicates an anagram (letters get chucked up).
'must'+'i'+'use'+'loan'='mustiuseloan'
'mustiuseloan' anagrammed gives 'SIMULTANEOUS'.
(Other definitions for simultaneous that I've seen before include "Happening at the same time" , "Done at the same time" , "absolutely together" , "Occurring together" , "Occurring at same time" .)