Is the character 跌 (to trip) a deliberate combination of 足 (foot) and 失 (to lose)?
Yes, it is a deliberate combination. But 「失」 is also a sound hint!
「跌」 (Baxter-Sagart OC: /*lˤi[t]/, to fall, stumble) is comprised of semantic 「足」 (foot) and simultaneously semantic and phonetic 「失」 (/*l̥i[t]/, to lose).

Compare several other characters in the phonetic series: